Where do you live and how long is your typical commute? Diesels are VERY slow to warm up in cold weather (they take forever in no-load conditions like idling in traffic), so if your commute is say five miles of slow driving, it will never reach full operating temperature. This is really hard on the vehicle! A diesel has no throttle plate, so vast amounts of cold ambient air are continually entering the engine under light load. Once the turbo is working - developing boost - the inlet air temp rises dramatically and the engine warms up.
You can help this by using a winter front and pre-warming with the block heater, but the fact remains that diesels simply are a poor choice for lots of short trips. Short trips (20 minutes or less) plus emissions equipment (DPF especially) equals major headaches and expense, and poor fuel economy from frequent regens. (For a classic example, Google "Mazda Skyactiv diesel problems")
Are you determined to buy new? If not you should be considering a 2006/07 Ram 5.9. The transition year to the emissions was 2007, so you will find some '07 models with the earlier engine.
How long will your road trips be, and is fuel range an issue?
I bought a 2006 Ram 3500 last September with just 78K miles, and it's a great truck, but I won't take it on short hops.
I think the Tundra would be a great choice for short trips while towing your 80, but if faced with a 1000+ mile highway trip that involved high altitudes and steep grades, a 3/4 ton diesel would be top choice. It's all about compromises - which features mean the most to you?
BTW the new Ram 2500 has major, MAJOR upgrades for 2014, with an all new air-bagged coil spring rear suspension. If you are looking at new diesels, this should be your first choice IMHO. Or the new 6.4 Hemi which should give super towing power and towing mpgs, and will run on 89 octane gas... Test drive a 2500 6.4 before you decide to go with a Tundra or other gas truck.
http://www.allpar.com/trucks/ram/2014-heavy-duty.html
BTW the higher end late model Ram interiors are drop dead gorgeous. The Tradesman, not so much.... I've not looked in a recent Tundra so I can't comment there.
John Davies
Spokane WA USA