YA CAN'T GO WRONG WITH EITHER.
Roadmaster seems to have a few less failures than BlueOx, but they're rare with both brands. Until recently, BlueOx was the more "elegant" of the two. Better-hidden base plates with easier install/remove of the draw bars. No cross beam. Roadmaster now has base plates and draw bars that rival the BlueOx designs.
We have Roadmaster and it's easy to tell how over built their stuff is. But that's a good thing when you're towing a couple tons. That said, the earlier Roadmaster stuff, square tube draw bars and that cross beam, is nothing I'd call User Friendly.
The Ready Brute has a great reputation and a built-in brake, but that isn't what you asked.
At least in Roadmaster, an "aluminum" tow bar only saves a few pounds since a lot of it is still steel.