Too your point, the 2500 is almost a HD working truck. The 1500 is not much of a truck at all. There really is not much of a comparison. The engine and transmission is only one part of the package. I have 2022 Denali with the 6.2L. I truly enjoy driving it and using for light truck work when needed. Load up the bed with 1,000 pounds of stuff and the tiny rear brakes become evident. It was purchased as a NY to Florida travel runner, and it does real well for that. After the recall oil change to the 0w-40 super car formulae the fuel economy has increased. Last trip home the truck did 21.7 mpg. Consider this oil discount cost is near $12/quart. Dealer is offering oil and filter change for $139.99 plus taxes. It takes 8 quarts.
Looking at new or fairly the increased maintenance costs for Diesel are incremental. If the gasser has to work hard to pull hills you should really run it on premium fuel. Pedal down, 4,200 rpm for extended periods works any gas engine hard. Adding the cost for premium fuel these days you catch up quickly to the price of Diesel. I often run the plus or mid-grade fuel as my trucks begins to run like crap on regular. I know that hurts it. Not only does it like premium but it also runs much better on the top tier stuff. During trips I use truck stops such as Flying J, Pilot, Loves. Get it home and fill it at Sunoco, it drives differently. It likes the good stuff.
