Sp: dispasionate eyes
So: wide opened eyes
Sx: bright eyes
Sx/So often have bright and intense faces. Sp/So often have cheesy, dispassionate/cynical and bovine but somewhat friendly and opened faces.
Also, my avatar.
So/Sx have a very recognisable face, and I can recognize them often just by seeing their face, especially the men, and they are very comon, I see them everywhere, but I find them quite hard to describe.