IMHO this is another caliber discussion. IF you have to shoot someone it is about shot placement more than anything else. IF you shoot both very well bigger is better, but only slightly. No handgun is actually able to stop someone w/a single shot. I normally carry an M&P 340 but on occassion carry the Ruger LCP and do not feel undergunned. FWIW I'm kind of thin too and find it difficult to hide a large handgun.

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Old Cop
LEO (Ret.)