This is a debate of opinions. The true answer is what works for your use. First and most important the tow vehicle must provide enough tow capacity for the boat, trailer, and equipment. Don't use the dry weight. There is enough information on Tugnuts to get a close estimate of what any model weighs. For example we have a C26 it is slightly heavier then a classic R27. There are many post of how much the R27 weighs going down the road. I use the weights posted to get a close estimate. When choosing a truck look at tow capacity along with the hitch rating and the requirements for that capacity. Many trucks ( the Silverado 1500 high country has a high tow capacity ( I don't know exact spec but it is 11000 to 12000lbs capacity) but requires distribution bars. Most 3/4 ton pickups have the higher rated hitch but not all, its in the small print.
If your trailering is down the street to the ramp a 1/2 ton will be fine. Our first year we used a Tahoe to tow our C26, I had to install air bags and use distribution bars. The Tahoe did a good job, pulled fine and hauled the boat up the ramp with no issues. I would never take it on the highway! The vehicle would pull it. I'm not sure it could stop it in an emergency situation ! There is a big difference in a Tahoe, 1/2 ton and 3/4 ton. 3/4 or 1 ton seems to be the preferred and honestly the right choice. The next question is Gas or diesel ? This too is based on how you are going to use the truck. Is it your tow vehicle and work truck ? Is it your daily driver and tow vehicle, do you use it on your farm, use it for your business and tow? What tows best ? My opinion diesel, you can't argue with torque. Will the gas engine tow the same load? Chevy, Ford,Dodge say it will. We tow with a Gas HD 2500 Silverado I purchased it new in late 2016. I wasn't retired yet and knew I had a few more years until I retired. The truck would be my daily driver and tow the boat 4 or five times a year with a max distance of 2500 miles a year. I couldn't justify spending 8 to 10 thousand more for the diesel. My plan was I'll buy the Gas truck now, use it, maintain it and when I retire we find ourselves doing much more towing I'll sell it and purchase a diesel. Since purchasing the truck I have put 31000 miles on the truck, of the 31000 miles the truck has towed the boat less then 4000 miles. While towing up a few of the hills in the smokey mountains I did see close to 3000rpm and my fuel economy dropped to 7 mpg. Most of our fuel economy stays at 8mpg average while towing. Diesel gets better but I'm not towing enough to justify the cost difference. The 31000 miles has cost less $500.00 in maintenance cost at the Chevrolet dealer. Oil changes, tire rotation and multi point inspection. I can't say from experience but I'm told the maintenance cost are higher for the diesel. The argument that towing all the time with a Gas engine will reduce the longevity of the engine, I would agree If I was strictly going to use the truck for towing it would be a diesel. The reverse situation goes for the diesel If the truck is your daily driver, light loads city and local driving this is hard on a diesel, it needs to be run. I honestly don't think there is a right answer. Its what works best for your situation. The most important point is safety, tow with safety.