Schuberth SRC Communication system for me.
Pros: Slick helmet integration that doesn't affect air flow or get in the way of anything, battery life claim is 11 hours (don't think I've pushed it that far, but have used it on 650+ km days), 2-channel (3-way) pairing (so you can pair with, for example, a passenger and another rider), easy pairing between riders and cell phone (I haven't tried a GPS or anything like that), built-in FM radio works pretty well, cell phone use works great, factory speaker recesses ensure everything fits well, and buttons are easy to use - with gloves on - after a little practice.
Cons: Only works with Schuberth helmet, pricey (see con no. 1), suffers the occasional "glitch" (turning off by itself, etc.), range is fine for passenger communication but probably wouldn't reach another bike if you were separated by a city block, and unless I'm doing something wrong, it won't charge while in use.
Overall I'm very happy, but this won't even be an option unless you're wearing compatible Schuberth helmets.