For a mess-around kart, I'd want the motorcycle controls simply because they'd be easy to set up with a dirt bike engine. But if I were going after some serious performance, in all probability I'd want to get one of them snowmobile-engine-powered beasts with car controls like they had on Top Gear. But for that kind of money, there are trillions of bikes that would be better for any kind of trail. And when it comes to bombing down fire-roads, what's wrong with an old Dart Swinger? Sure it's a four-stroke, but the damn thing only turns five grand, and they were in production for about five hundred years so you'd have a pretty cheap, easy-to-maintain, 180 horsepower redneck rally rig. Drop in a nice seat with some good lateral support, a good seatbelt/harness and a motocross helmet and you'd be pretty well set as well as you would be with the kart (although you could also drive it to wherever you're going so there's a big convenience factor).