After towing a mowing trailer with a 1/4 ton vehical for a while I say get the larger 1/2ton truck. The engine and trans in the ranger will stand up fine but the larger truck will handle and stop the trailer better. Fuel usuage will be about the same. The 1/2 ton will give you some growing room also. Which ever truck you get set it up with a good electric trailer brake system.
Knowledge is knowing a tomato is a fruit, wisdom is not using it in a fruit salad.