7 yrs. of FT travel fueling up at just about every type of station out there selling diesel...........NEVER had an issue with water/gelling/bad fuel so I don't consider it in a gas vs diesel issue.
Cool down time.....ha. That is only an issue when you have been pulling HARD and then decide to stop. By the time I have pulled down the ramp and gotten parked after a hard upgrade run the EGTs are already cooled down enough.
Another non-issue in a gas vs diesel issue
DEF.......don't have on mine BUT would be a concern that I would have to weigh (Cummins first year with DEF/SCR system on pickup---have it on other trucks) after I made other decisions???
Other decisions.......
What am I going to be using this truck for?
I tow FT.......so diesel was easy
IF I were looking to buy new right now and not towing FT but just for camping trips I would be looking hard at the gas/tranny combos available from ALL the players. (Diesel....probably would stay with the Cummins)
Stopping power.....non-issue in a gas vs diesel issue
Buy the truck that you want.
Then use it and enjoy it.