Your mileage won't be much worse with a 3/4 ton in the newer trucks, but your towing experience will be MUCH better.
Take for example a new Ram 1500 5.7L Hemi vs a 2500 6.4 Hemi. I have a 13 Ram 1500 Hemi 4x4 and avg around 16-17 empty. The new 6.4 in the 2500 is getting around 14-16 mpg, but has way more payload and tow rating.
If I were towing your trailer and didn't plan on getting a bigger one and needed the truck for a daily driver, I would look at a Ram 2500 6.4 Hemi. The 4:10 gearing would be better to tow, but hard to find without ordering the truck. The 3:73 will be fine for your trailer.
The best part is it won't cost you $65k. You can get a Tradesman crewcab 4x4 for low to mid $30ks.
Crown Dodge in Ventura has that truck in white and you could probably pick it up for about $33k. Or check Hunter Dodge in Lancaster.
I currently tow a 21' Ragen TH with my 1500 and it does OK, but the 2500 would be so much better.