Sync speed has nothing to do with the triggers. It depends entirely on the body you're using! (incase you hadn't figured that out by now :P).
Ummmmmm,, yes it does..
It also depends on the trigger/flash combo..
Using my RF-602 tx/rx I can get 250th second with my 430EX and 430EXII but only 200th second using my Nissin Di866 with both my 20D and 50D..
Using my 430EXs or Di866 I can get 250th second on camera or with my ST-E2..