I have a 3AJ XT600 Tenere, and have seen a couple of newish TT600s around. I am not an expert but the things I have picked up are that the TT600 is design much more for off-road usage (stating the obvious?) and normally lacks (in basic spec) some of the refinements of its XT600 brother (which is designed for dual/road use). So you may find a TT with or without an electric start, direct drive rather than a cush drive, less controls and lighting, but gaining off-road shocks, gearing, etc...(a high spec for off-road usage). I think you may be able to find the specs for each if you carried on with the internet search engines (however, hopefully somebody can also give you a good link?).
[This message has been edited by GeoffE (edited 25 September 2003).]