Whatever you decide, be sure you can get some ammo for it! I'd buy ammo at the same time, if not beforehand. New pistols aren't much fun if all you can do is wave 'em around saying "bang, bang".
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I child-proofed my house, but they still keep getting in!
I like the 4" 40 S&W best. A little harder to conceal but the power is better in my opinion and being able to get better accuracy from it helps in my decision.
I just run the 4" 40 better.
Try them all and get what works for you.