My 2 cents that probably isn't worth 1 cent.
PSA is a marketing genius and are constantly doing things to make them more attractive to the sellers. Now their actual product is complete garbage IMHO.
SGC until the recent changes seemed like a bunch of stoners that are happy with their product. They just didn't seem like they wanted to expand because that would mean more work. I love how cards look in their slabs and I believe they do the best job of grading cards by far.
I use both. PSA for resale and SGC for my personal collection.