I love the 4000 and think its the best all around choice. Unless you are running a car that weighs over 6.5 lbs on a very large track you shouldn't need any more motor. If you are a "one motor needs to fit all tracks" guy, the 4600 can be dialed back to work anywhere, but it won't be able to match the throttle response of the 4000. I've let quite a few guys try my truck at one of the local indoor tracks that have the tekin 4600 in their trucks already and a couple of them walked into the hobbyshop and purchased the 4000 on the spot.