I consider the Shield to be a slimmed down single stack version of the M&P9c. I own both and I think the 9c feels better in hand but both conceal well and the Shield has a slight advantage for hot weather concealment. I own and like both models so I think you'd be well served by which ever you choose.
Thanks for the input. I live in massachusetts so the max capacity i can own in a handgun is 10 rounds so capacity doesnt matter. Im thinking ill get a 9c now and get a shield for the wife when the become mass compliant