TT02, because it handles a lot better on low grip surfaces. M05 will just spin the wheels and understeer, but the 4WD car will hook up and hang the tail out. You can build the TT02 with extra ground clearance to be a rally car, and different wheelbases and widths to allow some of the coolest Tamiya bodies to fit (Capri, Celica LB, 911 Carrera, etc).
Great site for setting up your TT02: http://www.thercracer.com/2014/08/ta...-and-tips.html The single best improvement I made to my TT02 was putting 300k oil in the front diff as shown on that site.