As much as I want another Shield (still kick myself for letting the first one go), I'm leaning towards a 9c as well. It holds more rounds, comes with 3 backstraps, and you can find mags for it. The only con is that it's slightly thicker.
I honestly don't know if the backs straps are that big of a deal, IMHO. I'm sure after a little more time passs you will be able to find accessories for the Shield as it seems to be a very popular gun. Thickness does make a difference for concealsbility, but honestly if you have it covered, no one pays close enough attention to notice. Oh, and the 9c is also slightly heavier..... Hmmmmm..... Choices, choices!
If I were choosing between the two as an EDC, I'd still go with the 9c. but that's just my .