Living in Oregon with an abundance of mtns and hills diesel is the best way to go. I tow 9000lbs with a 12 CTD and would never want to tow that with a gasser. I towed 7300lbs of TT here with a 5.4 gasser and that was enough. The 6.2 and Ram 6.4 are way better than the 5.4 for sure, but any gasser is going to be shifting a lot compared to a diesel. IMO it's how often you tow as to how tolerant you would be. All that shifting is what eats into the mpg.