It's only with the 'face-cam' style portraits, Miiru might have more information (I was just expanding upon what I noticed when I took a look, purely out of interest).
Tested with
Simple3DPortraits.
Screenshots of the differences:
DX11/
DX9/
OpenGL
Also, while taking those screenshots I checked out the character creation screen and got these results:
DX11/
DX9/
OpenGL
Basically, OpenGL in the character creation screen behaved similarly to the DX9 results from ingame. DX9 was broken ingame, but fine on the creation screen. DX11 was fine on both.