Apples & oranges. I have both & like both. The P250 is much easier to shoot well, carries 15 +1 in 9MM, & most have night sights, all for about the same price as a 642. The Sig is not a pocket gun, however. The Sig needs a holster. The light weight is an advantage over your Ruger, but if you need to pocket carry, the 642 is much better suited for that. And there's nothing wrong with carrying a 9MM. If you shoot a P250 in both 9 & 45, you may find the 9MM better suited to quick follow up shots. I place 38 Spl & 9 Mm in the same category, they're both more than adequate for civilian self defense. I had a P250 in 40 S&W, didn't shoot it nearly as well as the 9MM (the bore axis on the P250 sits kinda' high in your hand). Like I said, I like 'em both, in the end, it boils down to "what you want it to do".