Let's see....
Off-road-
Trucks are easier to drive, buggies are faster.....
Associated cars are easier to drive, but Losi's will usually yeild better lap times and have more aggressive steering.....
On-road-
1/12th scales are literally "Fast and Furious", and believe it or not to race on a budget you can't beat a 1/12th car!!!
Touring cars are harder to set-up, but when set-up properly they can be easier to drive, but will never touch a 1/12th car on the track.
Losi- easy to set-up, easy to drive and fast as hell
Associated- more difficult, but when dialed it can be faster at some venues....
Tamiya- Tough as nails, easy to drive..... can be expensive
Schumacher- The perfect cars (I am a little biased)
Yokomo- Fast, harder to work on....
There are many others but these are the most popular.........