The 4 wheel down tow setup is more expensive than a dolly, but I believe more convenient as well. I don't have to find somewhere to store the dolly when I'm at a camp ground or resort.
Make sure if you choose a 4 wheel down tow arrangement (as it sounds you are) that the toad is 4 wheel down capable.
A new system could cost $2k or more. Remember it's not just the tow bar, baseplate, safety cables, wiring harness on the toad and flexi-coil from the coach to the toad, you also need an aux. braking system on the toad. Many of these components can be found used.
I personally like Roadmaster because they are 100% American made. I an not sure about Blue Ox.
FMCA #F431170, GS #822128658, Escapees SKP #112655
2012 Airstream Mercedes Interstate Class B