I have owned both. In 1942, living and working on a ranch, I bought my Colt .44-40 Single action, carried and used it until I enlisted in the USAF in 1950. When I became a civilian again I bought my Ruger .44 Mag Blackhawk that I have carried and used for over 50 years.
My Colt was a little lighter in weight and fired a 200 Gr cast bullet with a five inch barrel as I recall. My Ruger has a 6-1/2 inch barrel and fires a 250 gr cast bullet highr velocity. Both were (are) deadly on anything that I hit with them. I believe the Ruger is the stronger of the two, although I had no problem with the Colt. My Colt was well used before I owned it and it seemed to be looser, perhaps because it had been well used.
Both were well balanced and handy to use. Both were safe to carry and use on horseback. I have always been opposed to carry of any auto (semiauto) or double action revolver on horseback if you intend to ever have occasion to shoot from horseback. I know of a number of accidents by shooters of these types of guns when on horseback, even by mounted police. I know that there were times when I drew and fired quickly from horseback with both my Colt and Ruger when I almost certainly would have had an accidental second shot fired had I been carrying a double action. When you fire from hoseback in action you natuarlly hard grip the gun to hold it while controling the horse and the single action will not accidently fire a second shot without deliberatly cocking it.
If you practice fast draw with either the Colt or Ruger, with accuracy, you can be just as fast and accurate as with any double action revolver. I know since I have and do use both types and practice and use both. I carried my S&W Model 29 on duty for over 40 years as LEO when not on horseback and my Ruger Blackhawk on and off duty on horseback. I still carry and use both types while retired and working as a rancher.
I sent my Blackhawk back to Ruger years ago to have it modified for carry of six cartridges safely. Before Ruger offered the modification I carried it loaded with 5 rounds, just as I did always with the Colt.
Both the Colt and the Ruger factory grips are fairly good but I had the same problem with both. For my hands, both grips gave a punishing bruise to my second finger every time the revolver recoiled back and up. Also, for me, I had to concentrate on holding the revolver every shot with both the Colt and Ruger when quick draw and fire to keep the shots tightly where I looked. (This was also true with my Smith's.) It slowed me down slightly and the shots were not tight on target as I would have liked.
I solved this problem with my Smith's and Ruger Blackhawk by getting sets of Herrets Hand Fitted Jordan Trooper Grips. For decades now with all of my revolvers, my second finger does not take punishment and the revolvers point just where I am looking when I draw and touch the trigger without my thinking anything except concentrating on the the point (not just target) where I want the bullet to hit. At close range I don't even look at the revolver before firing. I often wish that I had been able to put these grips on my old Colt.
I do not own a Colt but I would feel safe with one today. I would select the Ruger over the Colt however if I were making a choice again.