I'll be shopping for a new (or new-ish) truck shortly for pulling a medium size trailer or 5th wheel. It seems like the vast majority of 3/4 and 1 ton trucks around here are 4WD, with jut a few 2WD...
If you get 2wd, make sure it has limited slip or a locker. That offers a lot of the benefit of 4wd without the problems of solid front axle (on some models), higher ride height, longer turn radius, extra weight and a $2,000 repair bill when the transfer case breaks.