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 Python 4" .357 Magnum | Colt 1968 Det. Spec. .38 Spc. | Ruger LCP .380 ACP | Daniel Defense M4V1 5.56x45 | Alpine M1 Carbine .30 | Steyr M1895 8x56 | Ruger 10/22 .22LR |1943 Izhevsk Mosin-Nagant M91/30 7.62x54R | Remington 870 12GA