Muds wear alittle faster than alterrains but not much. the basic differences are that mud clean out a bit better, sometimes make a little noise, and wear just a bit faster. the big wear differences come from boggers and swampers, but AT vs MT are basically the same.
Just my .02 - a friend of mine had a set of these and they wore way faster than my BFG muds (not commenting on BFG's particularly, but it served well for a comparison). When I had about 60% left, he was down to the wear bars, and our mileage was roughly the same. His were on a full size, mine on a Jeep.
We never compared tire pressure. Just my observations.
it does also depend on tire pressure, heat and the size of the vehicle. We had Cooper STT's on our Jeep and they hardly wore in the couple years we had them and that included wheeling, back and forth to Vancouver and daily driving.
On my fullsize Blazer I am running Cooper ST's a slightly better version of the STT. They aren't very noisy, ride real nice, look great, clean really good and havn'et noticed any irregular wear either. Tho I haven't had them on for long. (only about 6mos).
I also have Cooper Cobra's on my Rabbit, which are really nice tires as well. Cooper is less exspensive than BFG but has (I think) been around longer.
The mud tires I have had in the past have lasted about a 18 months before they were down to 40 or 50 %
Something to think about is that a tire at 80% is half way to worn out in my opinion. A mud tire at 50 or 60% is loud on the road and will perform poorly offroad. Many offroaders will replace their tires at around 70% to keep the performance up. I try not to run tires under 75%.