I'd nod towards the diesel, but it really depends on your priorities. To me, a 2WD truck isn't worth having, but that's me, because I use it regularly and plow in the winter. You may never need it, but I'm throwing it out there. As some others have said, how much you tow is a valid factor. The diesel will pull circles around that gasser and get better mileage doing it. Yeah it's going to need stuff, but there are other costs of ownership to consider, like that the diesel generally goes twice as many miles on a service interval. Oil and filters add up too, and a suggested change at 5-7K instead of 3K or so in the gasser is a pretty big difference. Also, my 12V regularly gives me 18-20mpg and easily pulls 13-15mpg with six tons of trailer behind it. I'm sure there are people on the internet who claim as much from their 318's, but I've never actually met anyone who came close to that. Diesel costs more, but the better mileage more than makes up for it for me.
That all being said, it does sound like the extended cab is a pretty important option for you. You're at least interested in going diesel, because you're here, so I'm not sure either of those trucks is "the one". I'd wait for an x-cab with a Cummins to turn up if you can.