[Jeff n Susan]

Strictly a personal preference.
The diesel will get you up the mountains a heck of a lot easier than a gasser.
I tow our 330RL with the F250 6.7 Powerstroke. It is my personal preference of a tow vehicle, and quite frankly, I wouldn't have anything else. It does the job quite well!
I have had a few gassers, and the convenience of the availability of gasoline makes them an attractive option, but anymore , diesel is just as readily available. I personally like the diesel for the performance. Yes, the maintenance is higher, but the trade off, to me, is worth it.