Lots of good info posted already. As noted, it depends largely on whether you want authentic Colt operation and handling, or a little more strength and far better durability from a mid-frame Ruger.
Modern Colts and clones are good strong revolvers capable of sending the RCBS 45-270-SAA (which drops about 285 grains) from 900 to 1000 fps while staying within 14,000 PSI. Brian Pearce has done considerable load development with this bullet for the various pressure levels of 45 Colt loads.
https://www.riflemagazine.com/magazine/PDF/HL%20246partial.pdfColts and clones are more prone to breakage of small parts such as the bolt and hand springs, but they are cheap and it pays to keep spares on hand. This applies to heavily-used blackpowder Colt clones as well. Music wire bolt springs are available (from Dixie Gun Works etc) which essentially eliminate breakage of that part, but they often lighten the trigger pull by at least a pound. This is fine but if your Colt/Clone has a three pound pull to begin with, take that into account.
As noted it is hard to beat a 4 5/8" New Model 45 Blackhawk for a lightweight, powerful single action. I've had several and with their aluminum ejector rod housing and grip frame, feel lighter in the hand than my 4 5/8" New Vaquero. But the NV balances better and while it's limited to Tier II.20,000 PSI loads, I like it better than any Ruger SA I've ever had. Ruger came very near to duplicating the Colt SA grip with the three-digit guns and they point and handle far better for me than any other New Model.
