For me personally, the "Q" dimension at the spindle is the important dimension, as that is adjacent to where my ankles need to miss. The dimension at the pedal hole is of little concern, for me, others will have different needs.
I do think it is good to know the variations between various bikes one owns, and the difference in dimension from center for the two sides. I try to set all my bikes up as close as possible. This has resulted in shifting the toe clip in or out to get things uniform between bicycles.