I am probably one of the few here who has used all three brands as a tow vehicle.
The truth is, in 2015 (only a few weeks away), all three make good trucks and I don't see any reason to rule out any of the brands.
You will hear posters on here tell you why one brand is the "best," but the reality is, there really is no best, just which truck you like best for you and your needs.
10 years ago, that wasn't the case and I would never have owned a RAM. Now, I love my RAM 2500 6.4L HEMI. Times change fast in the auto world.
Anyone who would not consider one of the Big Three brands is seriously doing themselves a disservice, IMO. Check out all of them. If you aren't brand loyal, you will also have more leverage when you start talking about price.
My rule is to never fall in love with a car (truck in this case).