Re: Which Ruger Single Six to get?
I think (with no disrespect) that Alpo is dating himself as an "old school paper shooter" relative to barrel length recommendations. Otherwise, he pretty much covers the subject well. Very long barrels are inconvenient, very short barrels are harder to shoot well.
A longer barrel and sight radius combination is theoretically better. But, theory and actual results are not always the same. For example I still often shoot Master level Bullseye scores. I see no significant difference between 30 shots @ 50 yards when fired from a 5" barrel Ruger of an about 10.5" barrel Czech Olympic type free pistol. As Charles. Askins, Jr. said: "Its 95% trigger control and 5% for everything else", assuming you are shooting decent quality equipment.
Another example that comes to mind is the Ruger model # KS47N Super BlackHawk with about a 7.5" barrel. This model was once popular at "club" metallic target shoots. It typically shot tighter sand bag rest groups than the nominal 10" barrel model that should have been more accurate. The exact reason(s) are speculative, but likely have to do with barrel harmonics.
My personal advice for practicing target shooting would be to buy a Bull barrel Ruger MK III Target model (unless you are lucky enough to find a late production MK II 5.5" Bull barrel, in excellent condition).
You can spend lots more money on a 22 target/utility pistol; but you will be paying for things like brand name, fancy wood grips, and refinements that only benefit Expert of better shooters a few points out of 900 for 90 shots. Most Ruger MK I, II,III 22 Target models are capable of shooting a National Championship Score if the shooter is. Most shooters (myself included, today) are not.
As for the "Single Six" models, most are "fun" plinking/utility type pistols. An Expert or Master Shot does not usually need a sand bag rest set up to see a significant difference in accuracy at 50 feet to 50 yards as compared to the auto-loading "Mark" models. I like to shoot as well as I can, so I do not own, use , or recommend them.
As for Blue or Stainless Steel. Usually, stainless steel offers an advantage only if the firearm will be subjected to environments that are likely to cause rusting problems, and you will be unable to keep your gun clean and oiled! Stainless costs more, but performs no better than blued (actually blackened) alloy steel. It reflects more light and is not preferred by most experienced target shooters.
Target shooters (muself included) who somehow have a stainless "paper puncher", often paint the top of it with "Ultra Flat Black" Krylon type spray paint to make them more suitable for competition.