Good point on the spare mags, I am guessing other things like holsters and mag holders might be more avail for the Sr9.
I agree that the Ruger is very underrated.... After a couple of years, the SR9 is still one of my favourite "nines" to shoot as it feels great in your hand and points back on target quickly, which to me, is a great reliable and accurate pistol. I haven't had the chance yet to try the Walther, but my mind can't get past the "elephant foot" grip. The PPX looks sort of like a mutant compared to the SR9.The ruger is much better than many want to give it credit for. It's a gun snobs nightmare. And mods to improve it are readily available. Can't speak for the Walther.
Had a PPX and it was a great gun, very accurate and no troubles at all. I agree with the mag problem though and that was the reason I sold it. You have to think of how available space parts are when making a gun purchase because sooner or later you will need some. I ended buying a M&P 9 (actually two, one CORE) and I love the guns. Best part is spares are available everywhere and walked into my local gun shop and bought mags for it