Of the choices listed...Security Six all day long. Within a coupe of weeks of turning 21 way back in the late 70's, a 6" stainless model was the second handgun I ever bought(the first was a Ruger MK1 bull barrel, I still have both). Through the 80's I shot PPC alot so it has had sh**loads of rounds through it, both factory and some very questionable reloads. Despite this, if I were to polish it up you would have a hard time telling it from new.
I still look for reasonable Service Sixes and Speed Sixes at every gun show and pawn shop I go to. I would like to eventually have one of each...just because