Towing that many miles my preference would be with a diesel. You will spend twice as much on fuel from my first hand experiance, both owing gas trucks getting 8.9 mpg towing, owning diesels and traveling with people who had both gas and diesels. The gas trucks were drinking roughly 2.5 tanks to one diesel tank of fuel, same size tanks.
Based on your choices You're looking at, 2500 hands down. Halfton option works ok for those towing 5% of the time and daily driver 95% of the time. There are a lot of post trying to convince people, they tow great, they tow ok and many need to upgrade their truck components shortly after to get it to OK. I get it as an option for someone trying to get a good balance out of a combination for mostly daily driving but not for what you describe.
