I guess I'm not sure what's being asked here. But if you already have the bigger truck, why not keep it?
We tow our trailer with a 1500. Our trailer is 6500 pounds fully-loaded (we got her weighed). Our (new truck) has a tow capacity of 9500# we have not towed with it yet so once we do, we'll see how it goes.
Our old truck had a tow capacity of 7k. It was okay towing but when we took it down to Disney and had to go on the hills there and in Tallahassee (where we're from), you could really feel the limitation of power. We didn't have any problems at all stopping but again these were hills and not mountains! The trip to Disney convinced us that we should get a new truck...we were previously going back and forth about it because our old truck still runs good and has ac (required in FL