Had a 2020 F350 6.7 PS XLT and now have a 2022 Ram 3500 HO Bighorn Mega. I tow a 15k 5th wheel weekend trips April-Nov for reference. Ram's interior is WAY nicer in my opinion on every trim. The HO Cummins and Aisin will out tow any 6.7 anyday and twice on Sunday. The exhaust brake alone make the Ram worth it over the Ford. Mileage on both unloaded and loaded is about the same. I'll give Ford the nod on cab space, miss my super crew cab size even with Mega Cab. If you towing over 10K Ram is the way to go...hands down. If your hot dogging light to light the Ford is a bit quicker in my opinion.
With all this said based off you needs why are you looking at an HD period? You're not towing much and you're concerned about fuel mileage. Get a 1/2 ton and call it a day. Likely Ford F150 with the 3.5 Ecoboost would be you best bet for towing and mileage. The Ram 1500's are VERY NICE inside as well and have a cab comparable to the Ford Super Crew. The 5.7 will drink fuel though... If you do go with HD and Diesel get a 1 ton/3500 as other have stated. Ignore "Tow Capacity" and look at "Payload" numbers. Tow capacity is totally a marketing joke... Remember payload on the sticker was as it rolled off the line. Very little fuel, no people, no gear, no hitches, bare bones truck. Payload disappears fast!