I have no doubt that a 4-Runner is a great tow vehicle for a TrailManor. But so is the Highlander, though I might prefer the 4-Runner if I lived in Colorado or if I was an off-road camper.
Frames on light trucks used to be built with steel channel stock like larger trucks. These days they are built with stamped and welded parts which are manufactured into welded frame units in processes very similar to unibodies. In any case, unibody vs "truck frame" arguments are irrelevant, except possibly for people who are planning to drill holes or weld something on a frame. Nobody should be doing that for trailer hitches anymore (trailer hitches are bolted onto manufacturer-supplied hitch mounting points).
Bigger vehicles need bigger engines. When you're not towing, it's nice to not be hauling around more vehicle than you need. A big V6 has surprisingly similar performance to a small V8, and I would suggest that combined vehicle weight, horsepower, and torque are much more important than counting cylinders.
Heavy tongue weights tend to overload rear axles and unload front ones. The Weight Distributing Hitch is mandatory for most of us: Reality is on the truck scale.
My numbers from the truck scale are here:
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