Im biased towards Ram but the new ones are full of problems being a new generation. They need to iron out the issues. Just got rid of a newer chevy for an older 4th gen ram. Chevy towed better but was expensive to fix all of its little issues. I concur that chevy needs its def kept more than half full or it has issues. Ram is better off road.
From the few fords I have driven, they were really nice, just expensive. Never towed with one. On any of the choices, you will not feel a 20' trailer with a diesel. I hardly feel my 30' trailer. Stay away from a 1500, just under powered, bed capacity and gas mileage will suffer. You could do a gas 2500 but mileage again will suffer.