My experiences aren't as extensive as others but so far I'm very happy with my 2018 F-150 with the 3.5 EB and 10 speed. Average MPG has been around 18 - 19 when not towing a 3500lb trailer. This is hand-calculated, not using the on board computer which was about 10% optimistic (there is a way to calibrate it though, which is nice: Now my hand-calculated figures match my on board computer pretty closely.)
Towing MPG is not good 9 - 13 but considering that the trailer is about 9' high and I'm pulling it over an 11,000' pass, I think it's reasonable. This is the same or a tad lower than what I got in my Suburban but where the Suburban struggled over the passes, in the F-150, I can stay in the left lane and cruise right by slower traffic, something I was NEVER able to do in the 'Burb. The 10 speed is great compared to the ancient 4 speed 4L60 in my 'Burb.
It's not all roses, some of the trim pieces are a little cheap and seem to be poorly attached (trim pieces at the bottom of the bed) and I still struggle with finding a good seating position. I can't decide if the seat is too firm, too soft, or just poorly contoured but it's not as comfortable as the Suburban, by a long shot. Long drives leave me hurting after a couple of hours and I need to stop and stretch. I miss the pre-set seat positions that my 'Burb had. The only other things I miss that the 'Burb had that the F-150 doesn't are a 4A position on the transfer case control (which I could have gotten with an upgrade to the Lariat trim level) and the rear wiper (though to be fair, the wiper on the Suburban pretty much only worked when it was warm, so it wasn't much help in the snow.)
On the plus side, I find the ride to be decent on 18" tires. MPG has been great considering that I'm running winter gas and mostly driving in the suburbs and city - around 18 average or a bit higher, the 'Burb was lucky to get 12 under the same driving conditions (10 - 11 was more common.) The 36 gallon tank is awesome and the capless fuel filler makes for quick and convenient fuelups. The 10 speed transmission does a great job of slowing the combo down when we are descending from a pass pulling the trailer. I love the quiet cabin and the audio system seems to have a good sound to it (I have an IPhone but I don't use Car Play because I don't like the way it "hijacks" the center display.) Remote start is a nice feature to have since I park outside (my garage space is dedicated to motorcycles.) In terms of space, I find the 5.5' bed to be perfectly adequate for my needs. In fact, for camping it's almost an embarrassment of riches in terms of space. With the topper on, when I put all of our normal camping gear in (stuff that absolutely FILLED the Suburban) it barely came above the bed sides, enough so that I have to actively discourage my wife from bringing more crap because "why not? We have room for it."
The crew cab is HUGE on the inside with way more leg room than the Suburban had.
I got mine used with 17k miles on it, and it's just under 24,000 now. It will be under the bumper-to-bumper through 36k miles and engine/powertrain to 60k. The only actual "issue" I have currently is that my left rear taillight housing seems to be leaking and when it does, water pools in the bottom and causes my lower turn signal bulb to pop (it's happened twice in the space of a month.) After the holidays I'll schedule an appointment at the dealership to have that taken care of under warranty since it's apparently a known issue.
I looked at the Ram trucks as well, and liked them OK but the wife didn't. When comparing the two, the 3.5 EB seemed to me to offer a more elegant solution to the problem of how to get decent MPG and decent power from the same engine than the mutli-displacement technology of the Hemi. The 36 gallon tank was also a big selling point for me. But it was a close choice - either one would probably have been perfectly suitable and the Ram definitely enjoys a "price premium" over a similary-equipped F-150.
The pitifully small 26 gallon tank (with no option for a bigger one) on the 2015 - 2018 GM trucks took them off my list as did the older-tech 6 speed auto. GM trucks also seemed to have an unusually high price point for the same year and miles, at least around here (Colorado.)
Overall I'm happy with my choice, at least so far. Given the cost I'm committed to this vehicle for at least the next 7 - 8 years which should take me up through my retirement, at least that's the plan. Who knows, maybe by that time someone will have come up with a well designed and reliable plug in hybrid pickup that will likely be my next rig.