TNX is very light, fast, strong and great racing truck, but Savage is heavyer, Stronger and better basher... 2 diffrent trucks wich I like best + the Revo.
I've been reading reviews on all of those trucks except for GS Storm Unlimited and XTM Mammouth. After what I've heard, its like this:

HPI Savage 25: Strong, 160cc fuel rank, great HPI .25 engine, great basher and ok racer.

Traxxas T-Maxx: Not very strong stock, very good basher, fast, smaller than other Monster trucks, ok TRX 2.5 engine and good racer.

Traxxas Revo: Strong, fast, great suspension, very good TRX 2.5R racing engine, good basher and great racer.

Tamiya TNX: Very light, strong, fast, big, great O.S. 18 CV-R engine, very good basher and great racer.

Team Losi LST: Strong, fast, big, great Mach .26 engine, very good basher and great racer.

Team Associated Monster GT: Strong, big, tough, great Thunder Tiger .21 engine, great basher and good racer.

I don't know about Storm and Mammouth.