The TC has new revised suspension arms with more tuning options, and the new rear diff is a MAJOR improvement over the previous version. The idea of the TC kit is to bring a revised car to market, at a lower cost than the previous. Things on the AME that were just "bling" were left out, and newer revised parts were put around the car to make it better on the track.
All in all I think it's a better performer. But you could have some of the very same benefits of the tc kit by changing to the new suspension arms and the new rear pro spec diff. There are a few other smaller changes around the car, but those two things seem to stand out the most to me.
-Korey