We have a tow dolly. It cost us $1300 and came with surge brakes. Price the cost of going 4 down. Base plate, tow bar, brakes, lighting, and installation. I can guarantee you it's a lot cheaper to go the tow dolly route. Then there's the issue that if you want to change cars or need to change cars, you will have to get another base plate and have it installed along with the lighting. Additional cost. Many cars that are towed four down also have special requirements, such as stopping x amount of miles and running the car...shifting through gears...etc. As far as easier....perhaps four down might be a little easier. But we can have our car loaded in almost the same amount of time as one does four down, but I didn't think it was a race anyway. When we are RVing, we don't worry about time. The only thing that some may find difficult is the fact that you will have to get down on the ground to hook the chains. If that's a big deal and you have a hard time doing it, then you might need to reconsider whether or not you should be driving a rig like that.
As far as storing it at the campsite, we are able to back our coach over our ACME tow dolly and cover most of it. When you get ready to leave, just pull forward a few feet and put the dolly on the hitch and you are ready to go.
I haven't read any stories on here about people tearing up their cars with a tow dolly. But have read numerous about their cars being messed up with four down.
As far as your question about what you can tow....we tow a 2007 Toyota Yaris. It weighs in the 2000 lb range and gets 37 mpg. It's my daily commuter car. Setting it up to go four down was going to cost me twice as much as the dolly. The car as 183,000 miles on it. It's running like a champ, but tomorrow it could go. If I went the four down and something happened to the car and I had to get a new one, then it would cost me another $300-400 for another base plate and then have to pay for the installation and having the lights set up...no thanks.