[pawpawdiv9]

Psa has more demand, especially in high grades, like you say becasue of their registry. People want the highest grade.
SGC does look better, espeically for older vintage cards. People use SGC for their grading and customer response.
PSA is better known for more money and for flipping for profits. Therefore has more demand. And PSa recently has a new hologram slab.
And you also touched another subject, PWCC is pricey auction, and always gets high dollars. Nothing wrong there, but noted many times is the bidding practices. They do have nice cards, and i look and bid sometimes.