Can't say I've ever heard of any of them personally. I've heard of ZD racing a few times before (I mean literally like 5 or so) in the years I've been posting here so can't say if they are good or not.

Personally I'd see what your LHS has parts support for, or if you don't mind waiting for parts how easy it is to source parts, and how many places stock them. Like for instance the HobbyKing RC's might look like great deals, but getting parts if hobbyking is out is next to impossible. Same with a few other brands like Exceed as there is like ONE distributor in the US that stocks things at questionable rates, and when they are out(and redcat doesn't have the same vehicle) parts are impossible to get.