As others have said the Sandking is the best in rough terrain due to the huge clearance.
The Kalahari is the best for climbing, you can go up near vertical slopes from a standstill because of it's excellent power to weight ratio and 4WD.
For races you want the Sanchez, it's just so much faster than anything else when you wheelie.
On desert and dirt tracks the bf Injection is excellent, good handling and great speed with decent clearance, plus it provides a lot of protection from bullets.
Personally I like the Merryweather Mesa because of the look.