I've raced both trucks in Factory Team trim, and they're both about the same as far as durability goes. The T4 is just so much easier to work on though, and it handles a lot better than the T3. That's not to say the T3 can't hang with today's competition, but the T4 is just a lot smoother and more predictable out on the racetrack.
The only thing I don't like about the T4 compared to the T3 is the lack of aluminum in the rear end. I know it makes the new truck much lighter but the T3 was a lot easier on motors than my T4 is, because on the T4 there's only the top of the motor plate that's really exposed to anything and conducts the motor's heat. The T3 had an aluminum motor plate which also doubled as a rear bumper, and that attached to the aluminum rear plate. The whole back end of the truck was a heatsink. With the T4, you kinda have to keep an eye on motor temperature.
If you're going to bash, I'd say stick with a T3, but if you're going to race (and at the top), look at getting a T4.
Faster Than Factory
On The EDGE Racing, est. 2001 - Home of the 524, the Silverado Slammer E-MAX6X6, and the Sand Dollar prerunner
Mike Budzien | facebook.com/OTE.TheMissile | RIVCO Products | The RC Corral | iRacing.com