Well... I'll bite... But I am bringing my pop corn....
About a year ago I started the same thoughts.. I had a 1/2 ton pulling about 7500lbs as well. I knew I wanted 3/4 ton but was not sure what direction. All my considerations are based on a 4x4.. I do need this for what I do.
1. Ability to pull (either way would work)
2. longevity of vehicle (I tow 4,000 or so miles a year and drive a total of 20,000 a year)
3. Fuel efficiency (its a big truck ain't gonna be no Prius).
5. (last for a reason) Cost
1. I expected diesel would be more powerful and most likely more enjoyable to pull.. But expected a 7 to 10k increase in initial cost. The gasser would still (IMO) pull BETTER than the 1/2 ton so either way was a win. We pull quite a bit through many different terrains.
2. gas engines last a lot longer than they used to, my plan was to keep the truck for a long time. I am not one to keep trading out at the end of the lease / loan. I want a truck for 10 years or more.
3. My 1/2 ton got 18 highway, 9 to 10 towing. My ride to work is 30 miles each way and is 90% highway. The gas 3/4 ton seemed to be (according to the internet) around 14 to 16 highway and 9 or 10 towing. The diesel was 16 to 21 highway and 12 to 14 towing (again, according to the internet). I will cut to the end here.. I did do the diesel and get 12 to 14 towing and 17 to 19 highway.
4. I do my own tire rotations, oil, and other simple tasks. The diesel does require a fuel filter every year (or so), more oil (mine is 2 gallons), and DEF. I will probably spend an extra 100 or 150 a year on maintenance. I consider that a wash. Spend more than that a year on Dunkin Donuts..
5. Cost WAS a slight factor, I am not cheap per se, but I do not want to pay more than I need to. An extra 7 to 10k is a lot of coin. BUT I also did not want to regret the buy.
When I hit the dealers I looked at the gas they were in the 48k range. They had the diesels for 49 to 50k range. I ended up looking at the above and my needs and got the diesel. I did have a gas 2500 for about a week while tow mirrors were added to my truck. I can confirm the 14mph driving.. I SUCKED fuel.
But I am not you, I do not know your commute to work, your amount of time towing / traveling. If I was only a one or two weekend person a month. I'd have sucked it up and dealt with the 1/2 ton. If I had a short commute to work I'd do the gas over diesel (they do not like short drives so they say).
While fuel efficiency was slightly important to me, I drive a truck, not a prius. So I was not getting wrapped up in it.. But for the 1k (for my case) increase in cost I did the diesel for the better mileage. If you drive 5 miles to work it might (in reality) take 10 years to break even on the saving of fuel so look at that realistically.