Another brand you might explore is Roadmaster. We had their 2000-1 dolly for a few years before towing 4 down. Like other dollies it is heavy, but not difficult to deal with. It has some nice features like attached ramps that lower for loading the car, steerable wheels to keep it inline with the rear wheels on the motorhome, lights, brakes, and storage compartments for the straps.
We towed our Buick LeSabre with it for 4 years before purchasing a Jeep Wrangler. We had intended to use the dolly for the Jeep, but reading through the manual we found it could only be towed 4 down or on a trailer. We sold the dolly to a friend who is still using it today. It's almost 20 years old, has nearly 200,000 miles on it, and still works fine.