So this is the opinion of a heavy equipment mechanic.
Unless your towing on a daily occasion I would go gas. The common gas engines have no problems going well over 200k if maintained well in pickup trucks. The cost of servicing a diesel pickup vs a gas pickup is the biggest thing. Your gonna have maybe 50 bucks in an oil change in any gas pickup if you change it yourself, while the cost of fuel filters drives that price up to almost 200 bucks a pop in a diesel. You can get away with running 87 in almost any gas pickup while a diesel needs much better fuel quality. The price of parts and used engines is much cheaper in a gas truck than a diesel.
Also God forbid something goes wrong in a diesel after treatment system out of warranty cause that will most likely be a big bill.
You will have more power in a diesel, and sometimes better gas mileage. I use my truck mainly highway miles, some offroad, and a little towing so my 5.3 liter Chevy does just fine. If I could afford a diesel maybe I would go that route, but maintenance is key to everything lasting.
In a camp setup it would depend. I've dealt with very few natural gas generators. I've seen the harbor freight gas generators run for a long time with no maintenance.