The one major advantage to a trailer is that one can back up anytime, anywhere, limited only by the driver's experience.
It is not recommended to attempt to back a dolly or a four down toad. Both dolly manufacturers and towbar manufacturers say "Don't back up!"
However, some say they do it all the time. I tried it once, with a Jeep towed four down. I will never do it again!
A trailer will also be equipped with brakes, as will many dollys. Nothing extra to buy. But then, in many, if not most, states, the only braking requirement for four down tows is a Braking Performance Law. Your state may be one of them. Mine is.