If your towing 10-12k that's a perfect load for a HD gas truck right in the max/sweet spot especially with 4.30 gears. If your pulling a 14-15k fiver than it would be time to consider a diesel.
A lot of the diesel guys give generic diesel is better responses without addressing the cost of ownership and hassle of owning a modern diesel.
I bought a new 2500hd in 05' and have done nothing but drive it, aside from changing oil, belts, and hoses.
When I bought my 06' dually used I could have gone diesel but I felt the gas truck was a safer bet, rather than buy the diesel only to find it needs a $5,000 injector pump or find out the Allison trans was abused and needs to be replaced. That would be downright scarey
03 Fleetwood 31g LS
06 Chevy Gas Dually
07 Yamaha golf cart
Looking to purchase a Georgetown 364 ts Mh in the next couple of years.