OP, if you are mainly highway driving, the diesel will get you better fuel economy. When I'm on the highway without my trailer, I'm getting 19-20 mpg at 70mph. I'm astonished that it gets such good mileage. Its way better than any gas truck I've driven. If you are on highway for good stretches, you are getting temps up high enough for passive regen.
Yes, maintenance is a little more involved in a diesel, but its not a deal breaker at all. I pay about $70 an oil change, not bad. Fuel filters every 15K miles is about a year and a half for me. I buy the filters on Amazon for about $90 for both and they are easy enough to change myself. The CCV filter I thought was 120,000 miles on DEF trucks, as they use EGR substantially less... but I honestly don't remember. The filter is $70 and its super easy to change.
Every thing else is the same, regardless of engine. Transfer case, cooling, transmission, etc.
Personally, if I was all highway miles and worried about engine durability and trade in value at higher mileage, I'd get the Cummins.