I know the Tacoma won't tow nearly as well as the F250. What I really want to know is if it's going to tear the truck up. I know how to properly take care of a vehicle, will monitor trans temps real time while towing just as in my F250 - but mechanical parts can only stand up to so much.
Towing with any vehicle takes it's toll. The higher the relative load, the worse it will be, obviously. I'm quite sure that even towing a 2500 pound trailer continually, as I do, will shorten the life of the truck. As far as any particular Achille's heel, I think the rear axle will probably prove to be the weakest link. It only has an 8" ring which is pretty small for the 4.0. The little Ford Ranger by comparison has an 8.5 I believe. Under load these little axles generate a lot of heat. When you hear about people dropping from 16 MPG to 10 pulling a load, you've got to figure that engine is working hard too. Mine averages about 13 towing. I regeared to 4.56 too, which did help.
There is no set answer. There are just compromises, and only you can decide what you need. If you do get a Tacoma, I think you have enough information to understand what you have signed on for. Your towing MPG will be poor. You will not be passing anyone. You will most likely not be keeping pace with traffic on hills. The truck will have a shortened life, although it may still out live a domestic. If you love the truck otherwise, and accept the limitations happily, then you are good to go.
I've towed 10's of thousands of miles with mine. Most of that in the western states. All kinds of conditions. That is with the truck fairly loaded and the 2500lb trailer. It has done well enough, but there is no way in hell I would expect more from it. If I had it all to do again, I would buy a Tundra. The more you tow the more little things start to bug you. Things like pulling up a grade doing 45 and coming up behind a truck doing 25. Then you hit a passing lane and have no ability to get around in the distance allowed. You go on mile after mile at 25. If I just towed once in a while I'd just chill and turn the radio up, but it really wears on you when you have miles to go and the day is getting long. A lot of it is personality too. Some people could drive all day at 25 and be happy as clams. I know a few,.....never passed anyone in their entire driving career. Only you can answer where you fall.