I bought an LC9, didn't care for the long DA trigger, and for me, my thumb tended to ride the mag release, and so it would drop the mag when shot to slide lock. I sold it to a buddy and bought a Shield and LOVE it. It is SO much more shootable than the LC9 it's not even funny. My buddy who bought my LC9 shot my Shield and traded his LC9 in on one.
That said, the LC9 is a smidge smaller and lighter, and for pocket carry and such that may give it the nod for some people. I still have my LCP and love it, but it's big brother never really did it for me. YMMV.