I posted this on another site as well. I have decided that the F150 I have is just not going to cut it with the trailer I have. Have an opportunity to get a pretty good deal on some 2015 350 Super Du...
I have towed my RV with both. Both will get the job done, just in different ways.
The gas engine will rev higher and get less mpg, but is cheaper to buy.
The diesel engine will rev lower and get better mpg overall, but is more expensive to buy.
I have had no regrets going from diesel to gas. I tow in the same areas you do as I am from western Canada too. Went to Banff and Waterton this summer. My 5er is about 12k lbs and is 37.5' long with 3 slides.