I was in a similar situation to OP. I was driving a very nice 2014 Tundra that didn't quite get the job done to my liking with my long trailer.
I was pretty set on picking up a used F-250 for 35-40k. I test drove both the F-250's and the Ram 2500. I ended up settling on the Ram and have absolutely no regrets. I was really quite surprised that the Tradesman offered so many options I didn't think I would be getting. I definitely preferred the Tradesman package over the XLT's I looked at.
I ended up just under $42k for a new 2016 Tradesman Diesel. The pricing on the Rams really does seem hard to beat.
They are both super nice trucks. I can't see that I would regret either one. The Cummins really does pull like a dream and the exhaust brake is simply incredible for pulling through the mountains.
The big Pros for me were:
Space under the hood(Huge advantage to the Ram)
Cummins :)
Exhaust brake
Entry level trim package seemed more generous on the Tradesmans.
Good luck Op, check em all out. They all make good trucks these days.