People trust CGC more the PGX because CGC was the first comic grading company and they had a large following of collectors who knew the CGC founders. CGC also had the Wizard Magazine account and did a lot of promotions through them and with them. PGX is also not as visible at cons as CGC.
PGX has since become synonyms with great product, value and customer service. I have used both but lean towards PGX. I have heard people say they send newer books to PGX and older more valuable books to CGC. I have also heard people say that PGX grades harder and have the superior holder.
Lets not forget that there was a 3rd grading company out of Texas called ACE Grading but they tanked early on while the other 2 continued on strong. PGX is committed to being a great company. Talk to the folks at PGX you will get that since from all of them.
Now its down to choice. Both have graded major KEY books and both have a major following. What do you want?