[sreader3]

Even beyond differences in the numerical scoring scales, I think comparing PSA v. SGC is apples to oranges since the companies seem to assign different "weights" to different kinds of imperfections.

For example, I have found that for PSA corners are a bigger deal whereas for SGC centering is a bigger deal. So if you have a crease free T206 with 80/20 centering and strong corners, PSA might give you a 5 whereas SGC will only give you a 4 (50). On the other hand, if you have a crease free T206 with 50/50 centering and soft corners, SGC might give you a 5 (60) whereas PSA will knock you down to a 4.

Just my personal experience.

Edited to add: I'm sure there are counterexamples; i'm just talking in generalities.