I personally run a B4 and love the car. My first car was a gold pan RC10. (go with what ya know i guess
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At any rate, if you can drive the cars, pick the one that feels best to you. Then, go with what has the most parts available. In central Florida, most everything is either AE or Losi. I've raced many a Losi, and have won against them and have lost against them. Its all up to the driver and which is best suited to their style.
I personally like the B4 myself. Easy to drive, but it does take a bit to drive it fast as it can get a little squirrely if you aren't careful.