I'd vote for a Ruger Blackhawk for its adj. sights and great value/accuracy/strength. As to price, hell, if you can afford $500, you can afford $550 and get a lot better gun out of the deal plus there's always the used market.
I own several Vaqueros, new and old, but unless they shoot to point of aim, they are a RPITA to adjust. The Blackhawk's adj. sights make all the difference. All of my Vaqueros have been "off" in windage to some extent or other, and fixing that problem is tough. Elevation is not a problem if you have a file and some cold blue, however.
I once broke the front sight off a baby Vaquero in .32 H&R trying to bend the front sight in the required direction. I managed to silver solder it back on and in the desired direction, but a better plan was to send the gun back to Ruger or to a known, good gunsmith to get the barrel turned for sight alignment.
I've also widened the notch on a New Vaquero in.45 LC to allow more light around the front sight blade and also to correct a 2" left point of impact. It worked out to perfection, but 2" is about the absolute max for my hold and the width of the rear strap vs. sight blade light issue.
As to multiple cylinder Rugers (45 ACP and LC; .357 Magnum & 9mm), they have a spotty reputation, especially the 357/9mm, for lousy accuracy with the 9mm cylinder. The .45 is less so, but you still have to deal with point of impact variations. For me, there is a 3" difference at 25 yds between a .45 ACP and .45 LC cylinder. Luckily, they both shot to the same windage.
As to availability and expense; locally since the latest panic buying spree, .357/.38 Spl has been a lot easier to find than .45 Colt/45 ACP; and somewhat cheaper if memory serves.
HTH's Rod