I just switched from Roadmaster to Blue Ox when I bought a new toad.
I think that they both make good products but, like foretraveler above, I really didn't like all that hardware of the Roadmaster hanging off the front end of my small car when not towing. Now, the Blue Ox hook up is nearly invisible once I pull the attaching pins.
That said, I prefer the Roadmaster tow bar for the sleeker design and slightly simpler operation.
If I could have arranged it more expeditiously, I think that I would have bought the Blue Ox base plate and a Roadmaster towbar with Blue Ox ends.
Since I have a coach with air brakes and a new car on the M&G fit list (actually a purchase criteria) I will shortly be installing an M&G auxiliary air brake in the new car.