Guess I'll have to stand up for the dirt-bikers and disagree with ya' here. I'm basically a street-rider, but I have some friends that have been riding off-road since just after they could walk (went off-roading with them once , spent most of the time with my face planted in the dirt). An experienced dirt-biker can make anyone on a 4-wheeler, experienced or not, look just plain silly. A dirt bike is lighter, narrower, more maneuverable, and usually have better ground clearance. They can go many places a 4-wheeler can't. No, you can't carry out your field-dressed deer on one, but you can carry quite a bit of stuff in panniers and strapped to the back. No, you can't mount a winch on one, but then again you don't need to. It's pretty hard to get a dirt-bike stuck.

The only big disadvantage that the dirt-bike has compared to the 4-wheel ATV is that it requires some skill. The 4-wheeler you can drive like a car.

Incidently, one of the afore mentioned friends that also rides on the street really likes the Kawasaki KLRs. Think he's owned, like, three of them now.