I'm not much of a Kahr fan. I have seen the embedded steel slide rails separate on a P9 my shooting partner had, then sold the new replacement pistol as soon as he got it. There has never been an issue with the Ruger polymer frame, and while one polymer may look like another, each has its own unique chemistry and P95s were tested with 20,000 rounds of Federal 115 gr. +P+ loads before they were introduced. Admittedly, there is nothing particularly challenging about the Federal load as it doesn't warrant a +P+ designation, IMO. I could make a 115 gr. JHP load that would equal its velocity at standard pressure. But since the Federal load did have an excellent street record, I guess Ruger thought it might be more recognizable for their testing purposes.
With the SR9, Ruger made a change to steel rails. The rear rails are embedded in the frame, but the mid rails under the chamber are part of the chamber-block like the XD/XDm. They're very substantial and it's a very strong system. They do continue to use polymer rails and in the SR9, they engage the front of the slide so the SR9 has as much or more engagement between slide and frame than any current polymer frame pistol. It is their best pistol design ever, if not the best product they've ever offered and the price is so low, it belies the design/build quality of the pistol. Triggers are very good and accuracy is outstanding. I already have an SR45 on the way because of my short experience with the SR9.