Well Ruger's "Bisley" isn't authentic at all. If anything it's grip frame is a variant on a 1920's-era custom Colt SAA known as the "#5".
The "New Vaquero" is the most authentic, but can't handle the monster 45LC+Ps. The "Original Vaquero" looks pretty authentic but is oversize in all dimensions, built on a 44Mag-class frame. BUT, in the holster, most people wouldn't spot the difference...even somebody who knows SAs in detail would have to look twice.
Now with all that said, the "Bisley Vaquero" is a mix of the classic-type frame with Ruger's Bisley grip frame, hammer and trigger. Ruger's Bisley isn't 100% authentic but it's well regarded for controlling big power. And if big power is where you're headed, you might want to compromise on authenticity. I can tell you that to people only moderately familiar with old west guns, the "BisVaq" is going to look pretty damned "cowboy".
To a purist though, not so much.