Im not much of a Ruger fan. Smiths are my favorite.
If I were looking at something comparable to the Ruger, Id look at a 3" Model 65 (or even a 2"-3" Model 10 or 64) if you can find one. Its a couple of ounces heavier than the SP, but they are great guns and shooters.
I dont have a 442, but I have owned a number of 642's, and still have one. They are good guns, if youre willing to practice with them, but the K frames are easier and more pleasant to shoot with, and also have an extra round to boot.
One thing you might want to consider with the Airweights is, the finishes dont seem to hold up real great to even moderate use. The 442's are a lot more noticeable too, as the contrast between the black finish and underlying aluminum shows a lot more.
My one buddy carried one for a number of years and looks beat to hell. My 642 has its share of nicks and chips, but doesnt show them near as bad. My sons 642, on the other hand, it considerably more beat up and really shows it. Not really an issue with function, but it something to consider if youre going to be using it regulalry.
Another option if it has to be a J frame, are the 60's. The have steel frames and are a bit softer to shoot. I still prefer the K and L frames over then, but Ive owned a couple of those too, and they are good shooters as well, but not as easy to shoot as the K frames.