To quickly throw in my admittedly brief experience with sensory deprivation:
This past week, after leaving a meditation center, I've found it incredibly helpful to just lock myself in a closet to meditate. It helps in some ways to "see" the vibes and catch hold of phase-shifts and so forth, especially if one's concentration isn't too terribly well-developed, like my own.
That being said, I can see (and have also experienced) how it's beneficial to meditate in a more exposed environment (within reason...or perhaps, if you're truly hardcore,
not?). There's something particularly gratifying about being able to just note or maintain relatively concentrated awareness despite the presence of disruptive noise. Or at least it's informative to witness the mind come up with all sorts of righteously angry ramblings

.
Anyway, if used skillfully, I believe both settings can help with concentration and confidence.
A sensory deprivation tank may be an interesting occasional experience that could impact practice some, but I would think one would have to do it consistently to gain any long-term benefit. Then again, it may help one cross a particularly difficult portion of the path in a one fell swoop sort of way...
Okay, just some thoughts - hope they're of some use.