If you follow the KZ1, KZ2 racing in Europe it seems the TM is on top. The KZ10B is the latest version.
IMHO the KZ10B is your best bet. I rebuilt a KZ10 a few months back and got a good look at it. The engineers at TM have redesigned the crankcase and cylinder from the previous K9 versions that will increase performance. The KZ10B has new pipe and some other changes that will improve durability.