Gets a bit confusing, doesn't it?
When the original model Vaquero came out in 1993 it was built on the same frame as the New Model Blackhawk, the only real difference being a simple blade front sight instead of a ramped front sight, the lack of the adjustable rear sight, and the top strap contoured to resemble the Colt Single Action Army.
In 2005 Ruger stopped making that model of the Vaquero and brought out the New Vaquero. About 10% smaller overall to bring it down to the same size as the SAA. There are other changes, but the New Vaquero was a bit smaller.
A few years ago Ruger offered a smaller version of the Blackhawk, specifically chambered for 44 Special and a couple of other cartridges.
To make matters worse, Ruger appears to have dropped the word 'New' from the catalog for the Vaquero, but it is still the smaller size.
To bring it to the matter of holsters, I have a holster specifically made for the older, larger style Vaquero that I wear on my gunbelt in CAS. These days a Colt sits in that holster. It sits down a little bit further in the holster, but not enough to really matter.