Lots to consider when getting a tow dolly. What type of brakes, surge or electric? Surge are cheaper and simpler, but are not as flexible in application as electric. Electric can be adjusted but require a brake controller in the MH. Ramp length can determine if your car will drag the front air dam when loading and unloading. Longer ramps make it less likely that your car will drag, but make the dolly harder to handle and store. The dolly should have some kind of passive steering, either kingpins or a turntable. Some dollies fold up which takes less space for storage, but adds to cost and increases setup time. Dollies come with different size wheels, bigger is usually better as less wear on the bearings. Check the speed and load ratings on the tires. Make sure the weight of your vehicle plus the weight of the dolly does not exceed your MH towing capacity rating. Some dollies include the tie down straps and safety chains, others do not.
When we started towing a car, we had a Master Tow dolly with surge brakes. Cost $1100 new. Took about 20 - 25 minutes to connect up and about 15 to disconnect. Storing the dolly when not in use was a bit of a pain. When we replaced the car, we went with something we can tow 4-down and sold the dolly. The Roadmaster towbar, baseplate and auxiliary braking unit cost $6000 with installation. Connecting the car now takes less than 10 minutes and disconnecting takes about 5. Despite the additional cost, I prefer towing 4-down. As far as driving the MH, there isn't much difference except the dolly setup was about 2 feet longer than the towbar setup so it made it less stressful to make really tight turns.