For a person who does similar amount of travel on both *A and Skyteam, I would say, at least ex-JFK, KE is 100 times better.
It really depends on where you originate.
From SFO and YVR, I would just take SQ over both KE and OZ and from LAX, I would stick with KE.
Summary
JFK/LAX - KE is better
SFO/YVR - Both are similar.
And I'm more of *A guy than ST guy.