Graded card value PSA vs. GAI vs. SGC

How much higher do you think a GAI card has to be graded in order to equal the selling amount of a PSA or SGC card? I know SGC is well recognized for pre-war but let's say for 1955-64 issues. Example: would you rather have a GAI 8 '63 Topps Power Plus or a PSA 7 of that card? Does an 8.5 make that much difference? Opinions are appreciated. I'm a PSA member and here are the cards I'm sending in. Will post scans tomorrow or Friday. Here's the list:
64 Topps NL RBI Ldrs.
63 Topps NL ERA Ldrs.
63 Topps Power Plus Aaron/Banks
64 Sox Sockers
64 Oliva
63(FB) Ernie Stautner
63 Camilo Pascual
63 Jim Coates
64 Don Zimmer
72 Joe Morgan x2, I think both have shots at 9s
55 Bowman Aaron
64 Topps NL RBI Ldrs.
63 Topps NL ERA Ldrs.
63 Topps Power Plus Aaron/Banks
64 Sox Sockers
64 Oliva
63(FB) Ernie Stautner
63 Camilo Pascual
63 Jim Coates
64 Don Zimmer
72 Joe Morgan x2, I think both have shots at 9s
55 Bowman Aaron
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