I run a 2013 Eco. It has been really good to me, of course, it only has 27k on the odometer. It gets used for pulling, hunting and times I need a 4 wheel drive. It has had zero issues. I pull a 28' fifth wheel and an 18' skeeter behind that. I was going to tune it but I have never said or thought "I sure wish I had more power". It gets 15 to 17 in town and 16 to 19+ on the highway and interstate. Gets 8.5 to 11 pulling whatever you put behind it.
I have never really ridden in a ford 6.2 or a Chevy 6.2 pulling so I cant speak of them. I have, however ridden in a 6.0 chevy pulling the exact same camper as mine and a very similar boat behind that and thought to myself, second gear pulling 50ish up hills at 5000 rpm is gonna blow this thing sky high!
Just like another poster said, buy what you like the ride of, when its unloaded. They all will pull better than you expect when the time comes to do so. All fit their drivers differently, get one that is comfortable.
This is mine. The water tank is 55 gallons and is under the bed in the front of the camper. I have a leveling kit on it (because of ground clearance for hunting) in this pic, but added an add a leaf to stop the sagged rear look a couple of trips later. With out the leveling kit in the front it would have never needed the add a leaf.