Yea Im in south central CO, close to CO Springs, we do dip down into the negatives. Have been using my FILs 2000 F350 7.3L extra cab long bed for last few weeks. My in laws didn't want me driving my 2wd F150 in the snow with our foster daughter. So from one extreme to another lol It was chilly one morning and I forgot to plug it in the night before, was a cold bastard to get it started but it did start.Lots of good, relevant stuff here so far. I would say location is another factor in owning a diesel. Living somewhere like CO like the OP, the power and torque of a turbo diesel is real nice climbing grades at altitude, loaded or empty. A gasser can do it no problem, but the diesel will do without breaking a sweat. On the flip side, dealing with a diesel as a daily driver somewhere as cold as CO isn't always fun, especially with a 7.3.
Im 31 wife will be 30 in a few months. Ive never been a fan of IFS GM trucks. Love the Cummins but like you said trannys. I need a crew cab. If I go with a dodge it has to be a mega cab, which is scares here. The Ford crew is nice and big. Buddy had one it was nice. He fit both car seats in it. He now has 2 car seats and booster in back of his 15 Cummins. Gassers are decent prices for even a couple years old and low miles. Its making me thinkWell like I said a 7.3 Superduty won't ride as nice as the newer ones in factory form, so you got some wrenching to do there. Extremely reliable trucks tho, especially with the ZF6 stick-shift. GMs all ride nice since they went IFS in the late 80s, not sure how I'd go about a 2" lift on those tho, cause it's small enough to be achievable by just cranking the torsion bar keys but that also tends to put more wear on the ball joints and CV shafts. Dodges, great engines with some not so great transmissions (pre-Aisin at least) behind them (so do your research there), and the pre'-2009 models always seemed to be somewhat lacking in usable space in the rear seat area... Kind of a pick your poison type of affair, they all have many good points and some so-so points, would be helpful to know how old are you (or your wife) willing to put up with?
Gassers are decent prices for even a couple years old and low miles. Its making me think
the mega cab on the Rams are nice but hard to find for sale
The coil sprung Suder Dutys ride like a Cadillac, shockingly smooth at least to me.
I grew up in trucks from the 60's & 70's with bench seats though.
Those Megacabs could be turned into a camper for the kids...when the seat is folded down the area is HUGE!