Well there is no doubt that if you are towing heavy and a lot the diesel is the way to go. They are an expensive option on the new trucks, but they really have power to tow. We just drove a dually in each of the big 3 and all are very closely matched. It's a matter of preference to brand. All will roast the dually tires easily...like a couple hundred feet if you want.
The 07.5's with the new emmissions stuff are having some small problems as owners learn how to drive them effectively.
Mileage varies on how you drive. If you insist on driving over 65 while pulling a heavy load, don't complain about gas mileage. In fact if you insist on driving very fast don't complain. These trucks weigh 7k or better some get up to 8k unloaded.
My 99 gets 19.5 around town, 21-23 hwy and I go 60-65 period. I can get 18 towing 8000# easy and 13-14 pulling a 16k 44 ft racecar trailer.
Diesel maintenance can be expensive and if you abuse it it can be very expensive. I measure everything in cost per mile. For example fuel costs 5-7 times what tires cost per mile. Again I drive to minimise cost per mile.
For a daily driver with no load dollars and cents wise a 1/2 ton gasser is probably a better deal. If you plan on 200-300k miles get a diesel. There are many people who have never done anything but normal maintenance on their diesels. Cool factor says get a diesel regardless.
If you like hot rods and only can have one vehicle get a diesel. For about a grand and a half you can have a hotrod that can dust most cars on the road and doesn't need a trailer to get to the races. Not only that you won't even get dirty installing the electronics. You can add 150 hp and 300 ft lbs so easy to most diesels and get better mpg to boot.