I don't have first hand experience, but in my own research I have found the following general consensus:

Poly-tone is easier to repair, can be sprayed wearing a cartridge respirator, and has a more vintage fabric-covered look. It can be buffed to a pleasant sheen, but not a high gloss. It also stains easier and is less resistant to solvents. (That's why it is easier to repair.)

Urethanes require a supplied air breathing system, give a "wet look" gloss, and are very resistant to stains and chemicals. They must be sanded off to make repairs. If you are willing to look at other Urethanes besides Aero-thane, you may also have a larger color palette to choose from.

FWIW, the factory-built planes are urethane coated.