That's kinda a funny question. They're both!
I bought the fronts used off Craigslist. I ended up ordering new rear wheels from Jeg's. I asked them to make sure if they were the TTII or the TT2.1. They siad they were just TTII's, but they weren't. It's hard to tell the difference unless you know what you're looking at.
The 1-piece 2.1 wheels are lighter and seem to have a nicer finish than the 2-piece TTII.