I use an inflatable when I do offshore racing. Just be aware that if you purchase an "automatic" vest water spray can set it off. They operate by having a tablet that dissolves when wet. If you're getting sprayed or the occasional "wave" when hiking out, then it's probably not worth getting the automatic. If you wanna shell out quite a bit of money you can look at the "hydrostatic" vests. These are automatic, but only go off when submersed in 5 inches of water. And of course there is the plain manual activation vest, but if you're knocked out they do you no good. Also the law in Texas at least, requires that a type 5 be on the person at all times. It's not like the type II or III where you can just have it on board.
I also do collegiate dingy racing. The most comfortable type III jacket I've found are designed for sailing. Although I suppose you could use them as a paddling vest. The whole goal is to get a lot of arm movement. Check out www.apsltd.com and see their selection of sailing vests. After spending most weekends racing in one of these I can testify to their comfort. If you do go with a non-inflatable, I think you'd be happiest with one of these.