Generally, the TT was more off road focused, less compromised with lights and rego stuff. I think some TT models might not have been universally road registrable. Basically, the TT was the “enduro” version, and the XT was the commuter/trail bike version. When I had a new TT600, it had a plastic tank, useless headlight, and tiny blinkers. I’m fairly sure the corresponding XT had a steel tank, larger headlight, and roadbike size blinkers. For example.
Or were you after specifics?