Pretty good summary, Driftwood.
I would add that despite the confusing names, there is a way to tell the guns apart, easily, IF you have them in hand.
ON the left side of the frame, below the cylinder, they say what they are.
Ruger new model BLACKHAWK
Ruger VAQUERO
Ruger NEW VAQUERO
I believe the new model lockwork was first made in 1973. Ruger did lose a lawsuit (perhaps more than one, I don't know), but it was a suit that from what I've heard, it was a suit Ruger should have won (a guy shot himself in the leg loading/unloading his Ruger in the cab of a moving pickup, so the story goes). Apparently the jury was unsympathetic to the "big gun maker", and Ruger lost.
Part of the settlement agreement was Ruger redesigned its guns, AND Ruger was, and still is REQUIRED to convert every "old model" (aka 3 screw) they get (for any reason) to the new model lockwork system.
There are other features of the new model besides the transfer bar that is different from the Colt system. There is no half cock position for the hammer. Simply opening the loading gate and that frees the cylinder for loading and unloading.
I have Blackhawks, a 5.5" Vaquero, a 5.5" Vaquero Bisley, a pair of 4 & 5/8" Vaqueros, and a 5,5" NEW Vaquero.
The New Vaquero with an inch longer barrel is virtually the same length overall as the 4 & 45/8" Vaquero.
Ok, I'm a Ruger fan. If they cost the same, I would choose a Ruger over a Colt. But they don't cost the same, not even close, and for what I want, and what I do, Ruger does it better, and cheaper.
ALSO, Ruger stands behind their guns, here in the USA. Colt CLONES made overseas (some of which are fine guns) are overseas, and even if they stand behind their guns, they are standing a long way off...
If you're looking for the exact old west look and operation, Colt is the one. Or a well made clone. The NEW VAQUERO is pretty close in size, and looks, but operated with the transfer bar system.
It all boils down to what you want, and what feels best in your hand, and out of your wallet.
Another thought you might consider is that there are a number of aftermarket parts & grips for Rugers, but if you put pachmayer grips on a Colt like I do my Rugers, being called a low down varmint for spoiling a Colt is getting off easy.
Of course there are lots of grips for the classic Colt SAA out there as well, as plain or as fancy as you might want.