I have had both, and my wife still has her LC9 (she won't shoot it, though, because it is the TALO Gold edition, and she says it is too pretty to shoot!

)
I didn't care for several things about the LC9:
1) the trigger
2) the LCI
3) the biggest thing for me was that it was too hard to detail strip the slide; I like to take out the striker/firing pin on my pistols and clean out the channel, which is easy to do on M&Ps, Glocks, and even some Rugers (like the SR9/9c.) I don't want to be knocking out pins, which you don't have to do on the Shield.
The Shield fits better in my hand, holds one more round (with the 8 round mag), and is just a better looking pistol, IMO.
So, I bought my wife and I both a Shield in 9mm, so we can share magazines, and since she won't shoot (or sell) her LC9, she needed a small pistol for her own use.