Flat tow is the easiest. We could disconnect/connect in a couple minutes. There will be folks saying "but then you can't back up". In 16 years of full-timing we never had an occasion to back up with the car connected so that is no issue. Have you ever backed up a trailer? Not fun all the time.
You do have to make sure your car can be flat-towed. There are towing sites out there that will tell you if it is or not - if you're planning to purchase a car. If you already have the car then read your owner's manual for the information.
We've volunteered in parks and saw problems folks had with having a trailer or dolly. Storage on the campsite is a big one. A dolly is awful if you need to prepare to leave and it's raining.
Good luck with your choice.