I've found that very few of them are good for rock cfrawling just because that involves such low speeds and the engine doesnt cool very well like that. I've got the Associated MGT 4.60. It has plent of power to climb just about anything. and is of course 4 wheel drive. I've dabbled with locking up the differentials, but found that the steering is very limited like that. The guys i run with have Revos and Tmaxxs, they turn much tighter, but they just aren't as durable. for waht we use them for.
I've recently gotten away from the "can i climb it" phase and I'm more set up for running on BMX track and going for air time.