I've seen the TC6, T3, Photon and the EX, among other cars be the fast car at my local track. There is some pretty serious talent in my area, and all cars are driven and can be fast. As for the T4, I have yet to see one at the shop or track, and Tamiya just isn't a popular chassis in these parts. I know the TC6.1 (haven't seen a worlds edition in person yet) is a fast car, as a few of the local fast guys stack them up against the xray's, Awesomatix, etc. I personally have a Tc6.1, and have been very impressed by the car, definitely not what I think is holding me back versus other drivers.
Good support in our area at local tracks and shops:
AE pretty much the cheapest and yet pretty durable
Xray very durable, does cost more than AE
Photon, seems to have the most brittle plastic although, maybe not since the Ex came out, as I see less breakage.... and its closer in price to the AE.