Today I have 2 slash 4x4's and a MERV on the way. The first slash I got was really fun for the first traxxas car I've ever had but eventually got to slow for me. Then, I got a 3s lipo for my velenion system and was shockers at the jump in the speed. But even still I wasn't satisfied. So after 2 months of money saving, I bought myself a mamba monster. The first day I put it in my car with 6s lipo, I blew my anacondas off the rims at 2/3 throttle. I was finally satisfied. But I wanted to get the 4x4 to 100mph, so I did with a custom gear ratio. Overall I would go with the mamba for speed and the velenion for bashing (because it is waterproof.) ya I know castle came out with a waterproof mamba and I've already heard of some problems. My choice would be the velenion because of it does have a good amount of speed and the reliability we all want.