The Springfield P9 was a higher end Tanfoglio pistol made in Italy but finished here by Springfield.
The current importer is European American Armory (EAA) who imports upgraded versions as the "Witness" line.
I was well pleased with my P9 and had excellent results with it.
Magazines are easy to get for the P9, but note that EAA no longer imports the P9 size guns. The new models use a larger frame so the same frame size could handle anything from 9mm to .45.
As I recall, EAA still sells the older original size frame magazines, and you can buy Mec-Gar magazines, who were the original supplier of magazines for these guns.
With that said, the S&W is a higher quality gun and S&W will still service them as far as I know. You'll have a much wider range of holsters, grips, and accessories for the S&W than for the P9.