Whichever current model has the longest overall length and blade length. The couple I've owned were so short and fat. Kind of like a big, heavy steel ball in your pocket. They are certainly cool and fit a niche market and are well built, but from a user standpoint the blades are shaped funny, carry is uncomfortable and sharpening would be a nightmare.
I don't mean to rain on your parade. Like I said they are cool knives. So.. if you're buying them to flip, get a fancy one, if you're buying them to use, get the longest blade (IMO) to balance out some of that fatness on the handles. The flipping action on the one I had was nice, compared to the one w/o the flipper. W/O the flipper it was kind of difficult to open due to the blade stop not really being in thumb stud position, if you know what I mean.
His carbon fiber is really nice, and so is his tumbled bronze finish on the Ti.
If you are getting on his books, I think it's worth it to give them a try. If you are paying secondary market prices.. tough call. I decided to go with a couple of Striders (insert your favorite brand here - ZT, Emerson, CRK, Hinderer) instead.
Best of luck.