Attention to single object vs. noting everything - Discussion
If you look closely, the breath is not a single object nor are the hands. 
Here is your answer regarding noting to stream entry: bp503s_Mahasi_Practical-Insight-Meditation.pdf (bps.lk)
Here is your answer regarding noting to stream entry: bp503s_Mahasi_Practical-Insight-Meditation.pdf (bps.lk)
Smarter and better practitioners will have better advice, but my brief take as someone in the midst of it:
Noting or some form of investigation into the nature of experience is what is required for deeper insights. You may be able to have them without a solid concentration practice, but the general advice is that concentration helps smooth out the process overall.
kind of like if you are operating a TV camera, you really want to focus on the camera work itself and not get caught up in the content you're filming. Without concentration you might frequently forget you're working the camera and might just start watching TV.
the momentary periods of concentration that arise from a solid noting practice can be enough for insights. But in the Pali canon the Buddha was all about investigation from the jhanas, too, so...
Noting or some form of investigation into the nature of experience is what is required for deeper insights. You may be able to have them without a solid concentration practice, but the general advice is that concentration helps smooth out the process overall.
kind of like if you are operating a TV camera, you really want to focus on the camera work itself and not get caught up in the content you're filming. Without concentration you might frequently forget you're working the camera and might just start watching TV.
the momentary periods of concentration that arise from a solid noting practice can be enough for insights. But in the Pali canon the Buddha was all about investigation from the jhanas, too, so...
At the beginning it is almost always very hard to keep attention on single object and why at this stage its just something you need to train. It might be at times easy but after you just got what felt like breakthrough of some sorts it might suddenly become much harder. This is quite normal and there are many reasons for that. Try to be mindful enough to notice these reasons. That said at this point its just something you will need to train.
Advice for concentration would be to not even try to keep your whole attention which you use during the day as its not what you should be training. The right concentration is having separate attention exists of only breath (or any other object) and that whole mess of attention system which you normally use should go to sleep and not even arise. Making you switch from using this default attention to is one of the goals of meditation. Its much easier to do it consciously and with much better effects than training your default attention for it to internally do the same types of operations - like it happens when person always use it and just forces themselves through this stage. Those types of issues mind can resolve in few ways are the worst because then it confuses people about practice in general.
This is important because if you train normal attention and then you will always have one more layer of "stuff" in between you and your mind. You should recognize such things and aim at going as direct to things as possible - usually involves splitting attention to more fine grained parts which arise individually.
At first you might need to use this default attention but shift out of it as soon as you can.
As for noting, insights etc. noting by itself causes certain agitations state in mind which causes it to then be oversensitive to everything and also do this noticing activity even when you are not meditating. Now agitation doesn't sound good and its not good but if you consider how lazy mind is regarding processing experiences merging everything in to some kind composite experiences it is actually better for it to get it little agitated. The key word is "little". Make it your goal to break mind by these practices and you'll regret it like many people did. This game is of doing enough for long time and not causing issues in mind. Also its more important to be observant in normal everyday waking experience than these meditation practices. They are the fastest way to instill in mind tendencies and to break through blockades, cause changes, etc. but
In time when you are careful with managing it you can find right amount of effort mind should put in to it to get best noticing performance with least issues. Of course it all stated like that sounds like lots of things you should understand and know how they relate in your meditative experience but thankfully you are practicing something that helps mind notice aspects of itself. At least if you put effort in to noticing important things like those you need to understand to optimize practice and its effect and not believe ascetic fairly tales that noticing something specific just long enough causes "awakening".
Also like with concentration the goal is not for your default mind to do noting. You shouldn't use the same attention which for concentration you should also not use. Likewise at first it might be hard to do it any other way but the goal is for mind to notice how sensations arise, to be able to deep in to them and know that this sensations is made from which other sensations and where-from they arise (which are subtle sensations which happen before the sensation you investigate - the timing here being the indicator) and not training yourself in to see yourself slap notes on sensations. The more concentrated attention of sensation (again - separate attention where the sensation is the only thing in existence) the less overall noise and its also more pleasant.
The goal of all that is to process all experiences with separate awareness which arise only to process single things . If you start being able to do that then you will be able to "penetrate" each experience and know how it arises and even modify how it arises.
Before you can do that you need to be able to notice things which happen in-between pulses that your brain generates while it normally operates so it might take a moment to arrive in there.
And to even get there you need to be mindful. Mindful as in true mindfulness.
It isn't noticing aspect of sensation just because apparently it causes awakening if you do that - that is asceticism.
You notice things you notice because you noticed something else and don't know what it is and how it arises and how it can be useful so you need more information. It really is less just sitting and doing boring practice and very active and fun activity. It is only not so fun when you expect too much - but even when ne day you had better meditation session than next day and you cannot hit the same jhana or whatever then just use it as an opportunity to study why you cannot do what you could day before. What sensations are there which were not before etc.
As for Stream Entry - it isn't any blip that makes you SE but you need to have right attitude and right insight. The so called fruition are technical phenomena which happens because whatever had to be done by mind was ready - and "what had to be done" in this case is not written in stone tablet somewhere in where they define rules for enlightenment but the direction your mind was taking develop new parts of brain capable of doing something more efficiently and then mind switches it defaults to these parts of mind. Depending on practice you do you can get wildly different result. And I mean the same e.g. noting can be considered many totally different practices depending on how you approach them. The only thing about this whole fruition thing is that its also something mind needs to learn how to do and doing it makes it easier to do it again. Still by itself not really Stream Entry - unless you have right insights, right attitudes, know what mindfulness is and removed fetters. Removed as in not "I don't believe there is self so I have no identity view" as this is not even scratching it. Heck, its exactly playing in to identity views. Just replace one view with another and call it a done deal. It doesn't work like that.
So now that you know everything about everything off you go to Enlightenment and beyond
Advice for concentration would be to not even try to keep your whole attention which you use during the day as its not what you should be training. The right concentration is having separate attention exists of only breath (or any other object) and that whole mess of attention system which you normally use should go to sleep and not even arise. Making you switch from using this default attention to is one of the goals of meditation. Its much easier to do it consciously and with much better effects than training your default attention for it to internally do the same types of operations - like it happens when person always use it and just forces themselves through this stage. Those types of issues mind can resolve in few ways are the worst because then it confuses people about practice in general.
This is important because if you train normal attention and then you will always have one more layer of "stuff" in between you and your mind. You should recognize such things and aim at going as direct to things as possible - usually involves splitting attention to more fine grained parts which arise individually.
At first you might need to use this default attention but shift out of it as soon as you can.
As for noting, insights etc. noting by itself causes certain agitations state in mind which causes it to then be oversensitive to everything and also do this noticing activity even when you are not meditating. Now agitation doesn't sound good and its not good but if you consider how lazy mind is regarding processing experiences merging everything in to some kind composite experiences it is actually better for it to get it little agitated. The key word is "little". Make it your goal to break mind by these practices and you'll regret it like many people did. This game is of doing enough for long time and not causing issues in mind. Also its more important to be observant in normal everyday waking experience than these meditation practices. They are the fastest way to instill in mind tendencies and to break through blockades, cause changes, etc. but
In time when you are careful with managing it you can find right amount of effort mind should put in to it to get best noticing performance with least issues. Of course it all stated like that sounds like lots of things you should understand and know how they relate in your meditative experience but thankfully you are practicing something that helps mind notice aspects of itself. At least if you put effort in to noticing important things like those you need to understand to optimize practice and its effect and not believe ascetic fairly tales that noticing something specific just long enough causes "awakening".
Also like with concentration the goal is not for your default mind to do noting. You shouldn't use the same attention which for concentration you should also not use. Likewise at first it might be hard to do it any other way but the goal is for mind to notice how sensations arise, to be able to deep in to them and know that this sensations is made from which other sensations and where-from they arise (which are subtle sensations which happen before the sensation you investigate - the timing here being the indicator) and not training yourself in to see yourself slap notes on sensations. The more concentrated attention of sensation (again - separate attention where the sensation is the only thing in existence) the less overall noise and its also more pleasant.
The goal of all that is to process all experiences with separate awareness which arise only to process single things . If you start being able to do that then you will be able to "penetrate" each experience and know how it arises and even modify how it arises.
Before you can do that you need to be able to notice things which happen in-between pulses that your brain generates while it normally operates so it might take a moment to arrive in there.
And to even get there you need to be mindful. Mindful as in true mindfulness.
It isn't noticing aspect of sensation just because apparently it causes awakening if you do that - that is asceticism.
You notice things you notice because you noticed something else and don't know what it is and how it arises and how it can be useful so you need more information. It really is less just sitting and doing boring practice and very active and fun activity. It is only not so fun when you expect too much - but even when ne day you had better meditation session than next day and you cannot hit the same jhana or whatever then just use it as an opportunity to study why you cannot do what you could day before. What sensations are there which were not before etc.
As for Stream Entry - it isn't any blip that makes you SE but you need to have right attitude and right insight. The so called fruition are technical phenomena which happens because whatever had to be done by mind was ready - and "what had to be done" in this case is not written in stone tablet somewhere in where they define rules for enlightenment but the direction your mind was taking develop new parts of brain capable of doing something more efficiently and then mind switches it defaults to these parts of mind. Depending on practice you do you can get wildly different result. And I mean the same e.g. noting can be considered many totally different practices depending on how you approach them. The only thing about this whole fruition thing is that its also something mind needs to learn how to do and doing it makes it easier to do it again. Still by itself not really Stream Entry - unless you have right insights, right attitudes, know what mindfulness is and removed fetters. Removed as in not "I don't believe there is self so I have no identity view" as this is not even scratching it. Heck, its exactly playing in to identity views. Just replace one view with another and call it a done deal. It doesn't work like that.
So now that you know everything about everything off you go to Enlightenment and beyond