Honestly, if that's all you really need a tow vehicle for, there's no way I'd even consider a diesel rig, its wayyy overkill, and that's true for quite a lot of people that have them. You'd be much better off with the toyota and be just fine, if it wasn't for needing a bed you'd have a lot more options. It doesn't sound like you're going cross-country or anything so you don't really need much.
I tow with a 2001 Silverado 2500hd, 4wd, reg cab,long bed, I use it tow move shit/haul crap more than I do to tow, but its never missed a beat and tow's 5-6k lbs easy. We even take it 7hrs south into kentucky towing a LOADED boat and bed, every summer, sometimes multiple and its been fine. It also sees a fair share of snow plowing in the winter.
good luck, but think about your commute factor and how little you'd actually be using the towing benefit of the bigger trucks.