RE: Ruger 9MM
I've had a LOT of experience with the P series Rugers. I recommend you choose 2 things-standard safety instead of decocker, and metal (aluminum) frame. The safety model will still decock when engaged, but will also act as safety, whereas the decocker is just that. I think the alloy frame choice over the plastic version is self explanitory, as some of the Ruger plastic frames do NOT have steel frame inserts for the slide to ride on. I don't remember the exact models which has plastic and which feature steel inserts.