well i have read that those two and the schumacher fusion or however you spell it are the fastest. I have a traxxas nitro 4 tec and it is very fast. But i wanted it to be faster so i got the 3.3 a high rpm exhaust and all 4 optional gears for the spur and clutch with an aluminum clutch. i haven't gotten to run it with the 3.3 yet but it was really fast with the 2.5.