If you elect to tow, the choice is between towing all 4 down or using a dolly. A dolly can be more hassle to unhook and hook back up and you have to do something with the dolly when not connected. But, with a dolly, just about any front wheel drive car can be towed on it. The dolly can have it's own braking system, so you don't have to deal with that on the car. If you have a car that can be towed all 4 down, you need the braking system and a base plate for the car that probably could not be used if you change to another car, at least not easily in the case of the brakes. The base plate, tow bar and braking system can (and probably will) cost more than a dolly with brakes.
With the dolly, about the only expense you will have when changing the towed vehicle will be for the lights(braking and turn signals), which may not even be an issue if you use lights that mount on the trunk lid, magnetically.
If money is not a problem, then using the 4 wheels down method would be the best way. You can always sell a dolly to someone else if you try it and it doesn't work out and it will be a lot easier to sell than the accessories (base plate, etc,) to someone that has the same type of vehicle.