one reason that hasn't come up in the posts is the cleaning of the bikes after muddin. The Grizzly is wide open making cleaning quick and easy. some bikes like the polaris would need a ton of plastic taken off just to get to the frame.
One idea for cleaning is spraying PAM under your fenders before muddin. Do this and mud just dosen't stick . some of them new spray on tire cleaners do the same thing.

 

If you do alot of mudding with the Griz I would recommend hoseing down your radiator mine gets just pluged with mud but still looks clean hose it out both front and back and you will see alot of mud come out of there