The hyper 8 is a good solid buggy and the 8.5 is an evolution of a pretty solid design. Pick one that is easiest to get parts for. Race the hell outta it, and watch the other racers. Walk around the pits, you'll see things that will speak volumes about the various kits. What's the fast guy driving?... ask him about it. Asking a forum like this will only get you conflicting views from arm chair mechanics. I suggest you do a little ground work. It's better to see something in person, in action, doing what you want it to; so you can make a better decision on your own.