I have towed with both gas and diesel. IMO, nothing compares to that raw, stump pulling power of a diesel. And the silly grin you become accustomed to wearing as you effortlessly cruise up long grades.
You are concerned about cost of repairs. Yes, that point is valid, but gas engines break too.
Diesels don't have the regular tune ups that gassers do. No spark plugs and other related parts to replace. I have friends in the gas guzzling department that try to convince me it costs more to maintain a diesel. I call horse puckey on that one.
Years ago it cost me $80 for an oil change, last one I did was $115. And it is always done at the stealership, not those drive in cheapo places run by incompetent monkeys. I want my truck serviced properly.
All I ever do is oil changes, fuel and air filters. Gas engines need that too.
I now have 418,000K on my Duramax. Yes, it has broke down. An injector pump at about 300K and the biggie was a head gasket at a 373K while towing through the Canadian Rockies in August of 18. That cost me a bunch to fix.
But let's say I was towing with a gasser and had the same breakdown. A head gasket in a gas engine will likely cost about the same to repair. No difference in the labor, still gotta remove a mountain of stuff to get at the heads. Perhaps a little more to fix the diesel...
In 18 I looked at the cost of replacing the truck. At that time new was around 80G for the same thing. That's a pile of money. I looked at used and I can't fathom how much used trucks go for.
I decided to fix and keep mine. It is paid for a long time ago. I figure I can put a lot of repairs into mine for the price of a new or used replacement.
Looking back now at the overall picture, I made the right decision, and I still have a diesel, inexpensive to maintain aside from a major mechanical failure.
And at 418K on it, it runs like a dream.