[Fred]

GAI provided numerical grades to trimmed cards. I'm sure PSA and SGC have done this but I'm guessing not nearly as much as GAI.

PSA has the largest registry and they've got a lot of collectors hooked on trying to build the highest graded set. I think people in vintage gravitate more towards SGC because there's less drama from them and they have a good reputation for having great customer service.

Beckett is fine but not nearly as known or popular as SGC or PSA. Personally, I liked SCD graded cards and I'll be happy to buy them at a discount because they were pretty decent at grading.