LOL, I have small hands but something about a flat grip does not work for me.
I had a Shield, pre-DECshooting, but did not like the flat grip... same reason I did not like my PPS (sold both). However, love my MP9c & Walther PPQ. Both have rearward (hump) curve that feels right to the palm of my hand.
Also, I prefer the mag versatility of the 9C with flat base 10rd, pinky rest 12rd, and XGrip 17rd. I'm gonna have to lose some weight before I consider tucking in my shirt using any Double Stack in an IWB holster. No problem with IWB & shirt not tucked in. I have a Bersa BP9cc (very reliable, never a malfxn), which is a very good deep conceal single stack IWB. Of course, if both 9C & Shield are a good fit, then I'd suggest plan on buying both. Why pick A or B when you can have C, all of the above.