I have always preferred 4-down. A dolly or a trailer is another piece of equipment...and in many places they have to be stored, sometimes for an extra fee.
But both (or all three) have their fans. The biggest problem with towing 4-down is getting the "right" car/pickup to do it with. This takes a bunch of research. And...DON'T believe the salesman. All he/she wants to do is sell the car. Research is up to you.
My toads over the years have been:
1- 1996 Ford Contour with a 5 spd stick.
2- 2007 Chevy HHR with automatic
3- my current, a 2011 Ford Ranger 4WD automatic