Don't be afraid of the gasser. It has it's benefits also. Compare horsepower to horsepower, that is what you use.
The 3.73 to 4.10 is going to be noticed at highway speed. The newer transmissions have so many gears and are engineered so well though that the difference is not going to be great, 1:1 tranny ratio about 400 rpm's, but if you're pulling the gasser will be higher rpm so as to be in the higher hp part of the power band. Diesel's make their horsepower lower in the rpm range.
I'd hope the diesel is worth more at resale, they cost around $10k additional.
I pulled a gooseneck trailer loaded with almost 14k # and a GMC 1 ton SRW and the 6.0 gasser and moved down the road at 70 mph easy, though it wasn't in 6th gear, but 5th.