Will also throw in my recommendation for the Sig SP 2022. Quite a steal for 430 dollars (the price I paid). Has a 1913 style Picatinny rail, a DA/SA system with decocker, and user-adjustable backstraps. I can't comment on quality compared to other metal frame Sigs since I have never shot one, but this gun feels substantially "nicer", higher quality than either of my compacts (Ruger and S&W) for less price. Negatives are the lack of accessories, although my hope is that will becomes less of an issue now that this gun is beginning to gain some notoriety.
Sig Sauer SP 2022 .40 S&W
Sig Sauer P938