I suspect the STT is a stronger and tougher tire. For dry climate off-roading like we have here in Socal, I'm not sure an M/T offers any benefit other than they look awesome.
The STT is the smarter choice, I think.
I went from Cooper AT tires to Patagonias because I wanted something that looked old-school. They are fun to have, but they are loud. Not sure I will get them again.