For sights, with the AmeriGlo I prefer the classic 3-dot. (SW-145). However - you mentioned that the OEM sights caught your shirt, etc. You might have the same issue with the AmeriGlos as they actually angle back a little bit. Doesn't bother me with any of my holsters.
See if you can spot the angle in this picture:
One other thing I should mention. TruGlo, another of the tritium sight companies, has not yet made a sight specifically for the Shield. However, many Shield owners are using the tritium sight used on the 9c or 40c -- or (not sure on this) it might be the same sight used on the FS M&Ps. (It could very well be that they are one and the same.) The rear sight fits pretty well with just a minor overhang. I had heard that TruGlo was coming out with a Shield specific sight as early as June -- which we have entered.
I have a TruGlo on my FS 9, and the AmeriGlo on my Shield. I actually like the AmeriGlo a little bit better because the white part is easier to see at dusk when the tritium green is not yet real bright. In total darkness, both the TruGlo and the AmeriGlo are the same green intensity. (I tried them side by side in a bathroom with lights out.)