Your #1 consideration when getting an 8th scale on-road is availablity of parts (this goes for any racing rc car).
All 8th scale cars are fast (even with a cheap engine). All of them have excellent set up features (Serpent, Mugen, Picco, SMP, HPI, Kyosho, etc..).
If you are new to 8th scale you will hit something and break something. If you break something and can't get parts for it what's the point??
Pick a car that your local hobby shop can support.