I had to buy a new truck last year after buying a new trailer. I thought real hard about the gas vs. diesel debate, but between a 11K gross trailer and a 13K equipment trailer, diesel was a no brainer. I have pulled my equipment trailer with my old 5.3L GMC and my neighbors 6.2L 2500 Ford and neither engine was really happy with the load. With the 6.7 Cummins in the new truck, the tall RV with a lot of wind drag and the heavy equipment trailer are both easy tows.
The main reasons that I went with Ram was the CP 3 injection system seems to be a little more reliable than the CP 4 in the Ford and GM, the Ram interior and infotainment systems are a lot better than the others, and Ram had a lot better pricing.
I do use this truck as a daily driver (16K miles so far) and have not had any problems out of it, though I have noticed that the back tires are wearing faster than the fronts - must be something wrong with the pedal on the right. As far as which truck is right for you, I don't think you could go wrong with any diesel 3500, and if you get the right hitch you can even get by with a short bed that makes it a lot easier to drive on a daily basis (at least you can fit in a regular parking space).
