To the OP, If you are set on a 1/2 ton then the Ecoboost with the max tow and HD payload pkg is your best choice period. I don't know anything about the Chevy 6.2L besides the fact I'm sure it likes to DRINK! But the Ecoboost will tow circles around the Chevy 5.3L all day long.
My trailer is 7500lbs, I'm within all my trucks ratings and it tows my trailer effortlessly. Would i rather be towing with a 3/4 - 1 ton diesel?? Absolutely! But my truck is my daily driver and i only tow my trailer about 8 times a year. The extra cost of owning a diesel is just not worth it for me. At least not now, maybe in the future when i have more time to travel and find a nice fifth wheel that catches my eye. But for now the Ecoboost is the perfect fit.