I think it really depends on your situation. My gas school bus gets about 6 MPG, but that's okay with me because I got it pretty cheap at an auction, and I also don't plan on doing a ton of driving around in it. IIRC the last time I did the math I pay roughly 50 cents per mile to drive it around.
My plan is to move only once or twice a year, with maybe a short trip here or there to see a music festival or whatever. Had I planned on driving around the country, it would definitely NOT have made sense to buy a gasser. Also as someone else noted, gas engines can be easier to work on if that's what you're used to working with.