Both are based on the CZ 75 frame. The slide is about all that is different.
WDButcher is correct regarding the sights. I had a T120 that had fixed sights (Front sight was staked and no hope for changing unless gunsmith did heavy mods)
There are some T120 owners that look to have CZ style sights. The P120 is pretty darn close to the CZ SP-01. You can read more and see my pics comparing the two here...
http://calguns.net/calgunforum/showthread.php?t=928523The T120 felt great and I would have kept it if I could have swapped the sights. I am not a big fan of the super small\low profile sights that come standard on the Tristar\Canik pistols.
BUT, Cajun Gun works has a nice selection of trigger upgrades and some fiber optic sights for the Tristar\Canik line. My P120 is there now getting some trigger work. If it comes out good, I plan to send my S120 in as well.
Best of luck with your choice!