First consideration is whether or not your car can be towed 4 down.
Second consideration is how long you're going to keep the car.
We had a 2000 Chevy minivan and didn't know how much longer we'd be keeping it, so we went with a tow dolly. Good idea for us: we're on our third car. I'd have spent a fortune equipping each of them for towing. Towing 4 down is the way to go, but a tow dolly is cheaper.
Depending on where you're going, a TOAD isn't always necessary. We were TOADless for a couple of years and could usually park close enough to any tourist place we wanted to go to.