First off, eliminate the HPI MT-2. The Rustler is faster, and has the newer, nicer engine. If you are planning on taking big jumps and going rock climbing, put the Rustler out of the picture. If you want pure speed and uncontrollable wheelies around a dirt track, that's the truck for you.
Now for the stadium (rock climbing, jumping, thrashing) trucks, I would actually either go with the Tamiya Terra Crusher. It has a nice low price tag, and many, many, many aftermarket hop-ups. The engine is bigger than the T-Maxx's (and on top of it, the new T-Maxx 2.5 engine is a hard bugger to tune). The Terra Crusher's reverse system and tranny are the best of any you will find today. Compared to the T-Maxx's reverse system, Terra Crusher's is indestructable. I have to say, the Monster GT is a nice looking truck, I just haven't had a chance to drive one myself. As far as the
HPI Savage .25, I have heard many many good reviews on that thing. It is fast, it has a nice layout, and it comes prepared RTB (Ready-To-Bash). Very nice truck. I'm a fan of the Terra Crusher still, but I believe it's just a personal preferance between that and the Savage .25.