The nice thing about magazine safeties are: 1; They give you the ability to "turn the gun off"! You can leave a round in the chamber, manual saftey off, and yet the pistol is perfectly safe, until you put the magazine back in.
2; It gives you an added retention factor in a fight! If your suddenly overwhelmed or your adversary has somehow gotten a hold of your primary weapon, you can drop the mag thereby giving he,she,they,or it a "dead gun". And it gives you time to draw your back-up and remove said problem(s)!
Between the M&P or P30: Get the one that feels best too YOU! Both of them work extremly well, and you can tailor the grip to fit your hand with either.
Go to a range and rent both and try 'em out if you can. Dale

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"Long live the S&W 3rd. Gen.!"