I have an SR22P and an SR40C. They are radically different pistols besides the difference in calibers. The SR22P is a hammer fired DA/SA trigger pistol that has a safety that also works as a de-cocker. It uses blow-back operation and has an aluminum slide.
The SR40C (or 9C) is a striker fired pistol that's trigger operates most like a SA only. It uses a locked breech system opposed to the blow-back and has a stainless steel slide.
The SR22P is a great pistol and wonderful to shoot. The SR40C is a great pistol and wonderful to shoot. But, getting the SR40C/SR9C and thinking the SR22P will be a great training pistol would be somewhat inaccurate. The SR22P is a great training pistol, but more in terms of practicing trigger control and other shooting mechanics.
However, it breaks down differently, its controls are different, it weighs a lot less and it feels different in the hand compared to the SR40/9C. IMHO buy them as great individual pistols, but not because of their similarities, or differences.
I don't think you can go wrong with the SR9C, but again - comparing either it, or the LC9 to the SR22P, or each other isn't entirely accurate. They all function a little differently and all have different purposes. The biggest similarity that I think matters, is that they are all Rugers. I'm not brand myopic, but I really like all my Rugers!