You'll have a hard time convincing me there are more than two or three flash memory factories supplying every major flash drive manufacturer. I'd say buy whatever form factor your fancy that you can get for cheap, and use it as intended: Data transportation. Don't put anything on it you couldn't afford to lose (either through data loss or physical loss) at the end of the day.
That said, my favorite form factor BY FAR, is the 'as small as possible' drives.
This waterproof pico-form factor 8 gig for $50 is about as good as it gets.
http://www.thinkgeek.com/computing/drives/a6d9/