Agree with you in general Leon that PSA gets a premium all else being equal in registry sets. That said, there have recently been a lot more examples like last night from REA where a SGC 4 Waddell throwing went for much more ($1,740) than a PSA 4 Waddell throwing ($1,050), and deservedly so.
https://bid.robertedwardauctions.com...e?itemid=96820
https://bid.robertedwardauctions.com...e?itemid=96816
Especially in popular sets, color/registration/centering increasingly means more than the grader and the premium for eye appeal keeps on growing.