Honestly, for me it comes down to looks and I think most SA guns look better with 5 1/2 inch barrels. That's what's on my Single-Ten and I'm looking for a .45 Blackhawk with another 5 1/2 inch barrel right now.
If it were me, I would go for the long barrel. I have a 7 1/2 inch single six, and it is one of my favorite guns. I guess I don't know what the Single 10 guy looks like. I don't know why. Unless you are going to carry it in your pocket, I would go for the 10 incher.
Upon further review, which means I checked out the Single 10, I want one of those. They have awesome sights, and 10 shots. No convertable, but I don't use my WMR cylinder much anyway. That is an awesome gun. There is a gun show here on Saturday. I am there.
If I was doing it , it would be the 5.5 single six with the 22wmr conversion.
22lr comes out subsonic with short barrels not desirable unless your using a suppressor.
MY pref for center fire is the 4.75-4.5 barrels I think they balance better and are faster pointing.
"Gun control: The theory that a woman found dead in an alley, raped and strangled with her panty hose, is somehow morally superior to a woman explaining to police how her attacker got that fatal bullet wound." L. Neil Smith
The problem with being stupid is you cannot simply decide to stop doing dumb things...