Last thing I'll say about the megacab vs any other back seat. Seams and feels like any other back seat the of any other truck all three big three included (in other words any truck not a Megacab) is that the back rest is very vertical and that is what makes it uncomfortable to me personally. The Megacab back seats have more of a angle to them then you can actually recline them back even further to a position of comfort for the individual person.
Now as far as leg room.... I think the Megacab wins here again. When we first got our 2014 2500 Megacab the first thing I was able to notice was the ability to get my self (300+ pound man) in the aisle between the seats to buckle all three kids in their car seats. (At that time my girl was around 3 years old and the twin boys were two, so we're talking about buckleing the full harness car seats)
Ok enough Megacab talk out of me. I realize your mostly interested in those two Fords but didn't want to see ya exclude the Ram because of thinking the led room and comfort was the same or less.