I run The GBC Dirt Devil XT and havent been let down. Ride good on the trail and will go through mud very well. Even works well for hill climbing in wet grass. Clean out good as well. I am very happy with them.
I have a set of GBC Grim reapers and love them. There 8 ply real stiff side wall.
Plenty of traction in mud, sand, gravel and grass. The nice thing is they don't rip up the grass unless you giver.
I had Carlisle ACT radials on my Can-Am and had 1,500 miles on it when I sold it and I swear they still looked like near new tread. Rode exceptional, great traction. Been on some sharp rocky trails at high speeds and not a cut or tear anywhere. I'm gonna get some to put on my Grizzly 660. If they last that long they're definitely worth the money. Don't do much mud so can't give you an opinion on that.
I have have used IP 589s, Kenda Bearclaw and ITP Terracross. I like the ITP Terracross fthe best for the handling and smooth ride and they work well in all terrain.
I have itp mudlites XL and have no complaints with them. Over all good tire. One of my buddies just got a set of the Zilla's and after a summer of riding they seem to be holding up great! My next set will probably be Zilla's as well. Pretty good bang for your buck since they're one of the more modestly priced tires out there for what you get.