I'd go for the E-Firestorm Flux. They are stronger than the Speed-T, and more versatile, they will go off road and do it well! The Speed-T has shortened shocks, so for real off-road use, these will need changing.
The E-Firestrom Flux is almost as quick as the Speed T too, and uses Castle Creations electronics (a Sidewinder and a 5700kV motor), which are proven reliable and tough. The Losi electrics (an Xcelorin) can be a bit temperamental.
__________________
|