I ran a mx51. All the way to Canada. (wore out a tire in 2 weeks). And ran a mx71 on the way back......So being that I was running that many miles back to back I could really concentrate on handling nuances...
Hands down n mx71. Works just as good in sand. And better on hardpaxk than the 51. Also the 51 had a bit of squirm when heavy cornering on hardpack. 71 did not...
Only place the 51 would outshine the 71 would be In fast going mud.. But if your buying either one for pure mud riding n your getting the wrong tires