Lots of votes for the Tundra. The extra power of the V8 is hard to argue, and so is the interior room, but for me I'd still take the DC Tacoma. If all you're going to tow with it is your M416, you'll be fine, but adding a supercharger would make it very nice.
My vote for the Tacoma is coming from spending time in similar places around Utah. If you're keeping your XJ, then some of this won't matter, but if you're going to retire the Jeep and use it's replacement where you're used to wheeling, then the Tacoma is just going to work better. Even though Moab is wide open on many trails, the approach/breakover/departure angles of the Tundra are going to be a pain. I know you are familiar with Moab so you'll know what I mean when I say you'll be dragging the back end of a Tundra ALL OVER THE PLACE. And there are plenty of steps/ledges that unless you have a large lift, the back end will drag so badly that you might not even get up unless you winch. The long wheelbase of the Tundra will be problematic on Moab trails as well with a poor breakover angle. Excellent skid plates will be a must since you'll be using them for sure.
You will still drag the back end of the Tacoma on Moab trails, but much less. Also, as a lighter truck it will be much more agile and less prone to breaking. The aftermarket for the Taco is MUCH larger.
It sounds like you explore the San Rafael Swell alot too. My guess is that the Tundra will handle most of those trails just fine as there aren't that many that are really difficult and tight. But I can still think of places in the swell that if I were driving a Tundra, I'd be wishing for something a little smaller. True, you'll be sacrificing interior room and that may be a bigger concern with your family. You'll have to weigh what is more important to you. I just know for me, that a fullsize truck, Tundra or otherwise is bigger than I want to drive on Utah trails. Heck, my 80 series Land Cruiser feels very big on some trails. You might consider an 80 series Cruiser as an option. You'll get similar interior seating room to a DC Tundra but room for gear inside the truck rather than in the bed, shorter wheelbase than the Tundra for better breakover angle. The LC also has a very strong aftermarket, you can get them with dual factory lockers, much less body behind the rear wheels compared to the Tundra.
So....after all of that, my vote is still for the Tacoma if you're after a truck. If you don't need the truck bed, I'd seriously look at the Land Cruiser. Good room, excellent comfort, very capable, tons of aftermarket support.
