While I think you could easily get away with a 1/2-ton truck, I have personally found that towing with a 3/4 or 1-ton is so much more fun, enjoyable and relaxing. I probably don't have nearly the tow experience others here do, but I spent most of my youth towing ATV trailers and such around behind my 1/2-ton '77 F150 without any issues, but never more than 4k pounds including the trailer weight with a 5200# truck. On the few occasions that I did tow more than that, I was wishing I had better brakes and a weight distributing hitch, as things were a bit less confidence inspiring with respect to sway and stopping distances.
I now tow with a 2014 F250 diesel (6.7), and it's amazing the difference. I'd used my mom's '99 F250 diesel (7.3 turbo) a few times and it did pretty well overall, but I certainly knew I had a trailer behind me. That said, the newer trucks do so much better with the modern 6-spd (and now 10-spd) transmissions, making much better use of the torque available IMO. My 14k pound tilt trailer weighs about 4400# empty, and I've had it at max capacity with about 1200# tongue weight and no issues for hundreds of miles back and forth over the Cascades, just hook up and go.
A friend of mine had a Superduty Powerstroke 6.0 (~2005), thought he could save money with a '96 F350 with a simple 7.3 and went that route, and immediately regretted it. He mostly pulls his '78 Bronco wheeler (~6000#) on a 24 ft gooseneck and what the SD handled readily pushed his '96 around like it was a compact truck.
I don't think there's a right or wrong answer to the question, but I'd get a 10k rated trailer for the type of use you're describing and then as modern of a 3/4-ton truck I could afford so that I could pull almost anything automotive that I wanted.
