It all depends on the kind of mud and the bottom. A rocky bottom with very light (almost muddy water) is a piece of cake with any quad as long as you dont drown it. If you get into the real wet clay mud, the type you loose your boot in when you walk thru it, any 2 wheel drive will struggle.

Tires also make a huge differance. I went from Sure Tracs to Shredders and although I like it better in the dirt, the new tires arent anywhere near as good in the mud.