Oh boy, you have opened a big can of worms here. My advice is get what people at your track run, and/or what your LHS carries. If it's still a toss up between all three, I reccomend the new Serpent 720. It's an incredible car right out of the box. No need for any hopups to be A main competetive. This car is VERY easy to drive with a stock setup. However, the other two brands, Kyosho and Mugen might be the same as I have never ran these. All three are incredible cars no matter what everyones advice is. You can't go wrong with any of them. That's why I recomended what people are running at your track. They can help you with setup, parts or whatever. In the right hands, all three...including the G4S you didn't list are ALL top of the line race cars capable of winning ANY event. Which all three/four of them do.
Good luck and have fun!!!!