If you are going 1/2ton, I assume this is fairly light duty (ie: you are towing 3k miles per year not 30k miles per year). If you are doing a lot of towing, I would look to bump up to 3/4 or 1 ton and then the ecoboost is off the table as an option.
So assuming 1/2 ton, I would go with the ecoboost. Don't expect great MPG when towing...it takes fuel to generate power.
But the big reason is performance in the mountains should be better. When you are at 5000ft, you can expect around a 15-20% loss in power due to thin air from the V8... but the turbo in the ecoboost will mean you have lost almost nothing as it force feeds air into the engine to compensate.
I wouldn't get too hung up on rear-end ratios...with the newer 10speed transmissions, the truck can select an appropriate gear to convert HP to torque at the wheels.
PS: If you do want to look at torque, you need to look at the torque curve not just the peak number. A slightly bigger maximum torque doesn't prove anything if the engine can't get up to the RPM where it generates the max. This is also a plus for the turbo as it allows for better low end torque.
On a related note, either engine is probably plenty but make sure the payload (not tow) ratings support 7k lb trailers...you could easily be looking at 1000-1100lb hitch weight plus if you carry stuff in the truck, you could be at 2000lb really quick and the lighter duty 1/2ton could be overloaded even though the tow rating is in limits.
