There is sod all clearance between my fork brace and nearly too big tyre so proper mucky nutz only lasted one ride before they got ripped apart. The one I made out of 1mm polycarbonate has lasted 6 months with just scratches, if they made them out of stronger plastic I wouldn't need to make my own but then they would sell fewer. For fairness the original lasted ages with a smaller tyre and more clearance and they are great.
The Mudhugger front is pretty obviously Mucky Nutz inspired, or looks that way, but made from much thicker moulded plastic, possibly slightly less clearance as a result.
I've found the XL fine in the Peak with a RS Rev and 2.5 Minion DHF, but then there's not much claggy mud. I holed one on my singlespeed at a quagmire Mayhem though in the space of six or seven muddy laps. I guess it depends somewhat on the type of mud