If I had ever seen one in real life, I'd say the Shield. As much as I love Ruger products, the Shield seems to be an all-aces pistol. The only exception is if the LC9 feels significantly better in your hand and points more naturally for you.
I have had a wonderful experience with my LCP and my buddy with an M&P40 has had a great experience with it. You can't really go wrong.
Beretta PX4 .40 S&W - Beretta 92FS 9x19 Para - Rock Island Armory GI 1911 .45 ACP - Colt 1968 Detective Special .38 Spc. - Ruger LCP .380 ACP - Daniel Defense M4V1 Carbine 5.56x45 - Alpine Industries M1 Carbine .30 - Steyr-Mannlicher M1895 8x56 - Ruger 10/22 .22LR - Remington 870 Express Tactical 12GA - 1943 Izhevsk Mosin-Nagant M91/30 7.62x54R