27 Is the 40 twin to my 26. It's all what you shoot the best! And what you are comfortable with I really dont think any bad guy is gonna know the difference between a 9mm or a 40 if it hits its mark! I use to swear by a 40 until I shot a 9 and I just shoot the 9 so much better and more comfortably. Was kinda of funny how it happened because I was looking for a 17 or 27 when I found my 26 and I passed it up because I didnt want a 9mm a couple weeks later I went back to place and saw it again and the guy kept coming down and down until I finally couldn't refuse it. I had every intention of flipping it for a new gen 4 17 (I still had my 22 at that time) and when I shot it I fell in love with it and still have it and still carry it everyday after all these years.