The M&P9c and the Sheild serve two different customers.

The Sheild is meant for ultra deep concealed carry.When you're carrying a gun in a private business that's run and staffed by full time hoplophobes,or in a similar sensitive area where its legal to carry but a printing gun can cause cultural complications;you had best believe every millimeter of mass counts.

The M&P compacts serve as backup weapons to their full size counterparts.They're great for that purpose in Law Enforcement,but for a citizen its just big enough to not be truly concealable like the LC9s and whatnot.

The women see the value instantly in something like the Shield;The modern fashions are unforgiving for women looking for a concealed carry setup.Skin tight jeans and shrink-wrapped tees mean a gun that's the size of an iPhone would print OWB.If there is any category of citizen that needs to bear arms,its women.