I have a 9c but find that it is not much more concealable than a FS. For me, there are two levels of concealment - holster or pocket. If I have to wear a gun in a holster, then I can typically conceal a FS as well as a compact.
I was ready to buy a J frame revolver to pocket carry when the Shield came out. Got the Shield and I routinely pocket carry it now.
To me, the answer to the OP's question is fairly simple. If concealment is the most important issue, then get the Shield. If firepower is the most important issue, then get a FS pistol. I think that the Shield has made the 9c obsolete. The J frame is too hard to shoot accurately, unpleasant to practice with and too hard to reload.
I wouldnt say obsolete by any strech. The 9c/40c will continue to be as popular (maybe more) than the shield. I just think if you want a weapon with Capacity,Power and concealability The 9c/40c is the way to go.