I'm a 3/4 ton fan. We tow a 7K lb TT with an F250 with 4.10 rear end. Been all over the place in 7 states in the west and has never left me wanting for more out of it. Used to tow with a 1/2 ton. No comparison. The 3/4 ton are beefier all round, although the newer HD payload/max tow 1/2 tons are allegedly pretty good. Our F250 was a lease return and has been very reliable. Until you've towed with both, you'll never appreciate the difference.
I would avoid getting a 4x4. They reduce available payload capacity, are 5-6" higher above the ground (so annoying) and there's more "stuff" and cost to maintain. A longer wheelbase is better for sway & handling. A higher (numerically) rear end is better but can reduce in-town gas mileage.
Old vs. new:
