Some of this comes down to how often and far you will tow.
- If you only go to a nearby park 50 miles away a couple times a year, it's level ground and prefer the 1/2 ton truck, you will be at or slightly over the limits but it should be fine.
- If you will be towing a lot or in the mountains, the durability of a 3/4 or 1 ton truck will pay off in the long run both in comfort while towing and durability.
The manufacturers have duty cycles and with the 1/2 ton at the max loading, I'm betting the duty cycles assumed are a lot less than with a 3/4 or 1 ton. So push it to the limit once in a great while you won't see much in the way of issues but push it to the limits regularly, expect a problem child of a truck if you go with the minimum truck.