The branch doesn't really matter, the individual chips all come from the same small group of manufacturers.
What's most important is to find out whether it uses MLC (multi-level chip) or SLC (single-level chip). This is one of the more important things that affect throughput and longevity.
MLC is a lot less expensive to manufacture, but is a lot slower than SLC. These also have lifetimes in the 10,000-100,000 range for writes.
SLC is a bit more expensive, but is very fast, and has lifetimes in the 100,000-millions range of writes.
What really sucks, is how hard it is to find out which style of chips is used in a $40 flash drive.
As for the whole U3 thing: they all come with a "remove U3" utility that will reformat the stick to be one large, plain, USB drive. I have a bunch of Cruzer Micros that I've removed the U3 bits from.
It'd be really nice if you could test drive USB sticks in-store to see which ones work best.