all depends on what you really want from the truck.
shrunken 1/8ths
losi scte is built like a tank, but is heavy compared to the competition (which can help
)
hong nor is similar to the losi but lighter all round and not so stable as standard due to the electrics postion, but can be turned into a great truck
hobao, very similar to above having seen a couple going they are very good once setup
Race designed trucks
Ae sc10 4x4, my truck of choice
very strong, nice and stable, some good tuning options. can be high maintenence (doing diffs trackside wont be easy). can be too light and get pushed around.
Durango
. current class leader very fast and nimble, yet to see one on the dirt though (roll on coventry national). have seen a few temperamental issues and breakages, if you already have saddle packs then its perfect.
there are a few others (lrp, ansmann, maverick etc) but not the best if your really going to race it,
best bet is try and have a go with the ones you fancy, that way you already have an idea if it suits your style