Welp, OP, with 60+years of experience owning pickups, towing trailers, hauling firewood and hay, moving out to the West coast and back, and moving around Montana, all I can recommend is go ahead and get the 3/4 ton with diesel engine NOW!
Chances are you WILL get a bigger trailer (IF you stay with TTs, that is.) and you will eventually need that bigger truck. I made the mistake of getting rid of my 1 ton and replacing it with a 1/2 ton a few years ago. It was a nice truck, but it just didn't have the towing capability I wanted. Now, I am back to aq 3/4 ton diesel. Yeah, it rides like a truck! That just proves to me that it IS a truck.
Just to throw crud in the game, once you have decided on the size of truck, then the question becomes "4X2 or 4X4". Well, I got by just fine towing a 32 foot triple slide fifth wheel all around the West with a 1 ton 4X2 with limited slip differential. I even drove that truck on skid trails in the mountains. Never got stuck. Now, however, I have a 4X4. The reason why is quite simple: 4X2 trucks are extremely difficult to find around here.
Ultimately all these decisions have to be based purely on personal preference, just like the make of truck. Personally, I prefer Dodge trucks (no, not Ram trucks, they are too new and expensive).
Good luck in your search.