Hi James!
If you hadn't achieved the 1st jhana yet, I would have suggested doing that first (it make me just enjoy meditation that much more), but since you already have:
I asked the same exact thing on a different forum a little while ago, and they suggested developing both at the same time, e.g. one in the morning, the other at night, or even both in the same moment.
After doing both at the same time for a little while, I found that I tend to prefer one over the other, depending on my mood. For some reason, now that I'm in the thick of insight meditation, the jhanas just feel plain unpleasant to me (and just the opposite was true when I was primarily doing concentration meditation), so I don't purposefully seek them out, but if they naturally come up during meditation, I just note them and don't suppress them or anything. On the other hand, when I was in the thick of what I believe was the "Fear" stage of the Dark Night, I CLUNG to the concentration states to alleviate my fear and they really helped get me through it, like a security blanket or training wheels.
If, for whatever reason, you want to attain the rest of the jhanas first before continuing with insight, that's fine too, imo; it won't take much time at all--perhaps even just a week or something, so don't think you're gonna have to spend a year doing just that.
My own plan is what Daniel recommends--to work on concentration between "paths"--since I don't feel particularly jhana-clingy at the moment. So basically, I guess my suggestion is do what you feel like doing. ;)
Hope that helps!