FYI: You don't need to join PSA just to grade cards. Just print out non-member submission forms. Here is a link:
http://www.psacard.com/submission_ce...onmember.chtml
I also agree with the above poster. PSA for post-war, SGC for pre-war. (with the exception of t206, PSA for that too). PSA will often over grade pre-war cards when compared to sgc; however, PSA is tougher on post-war cards than sgc. SGC seems to be consistent in there grading regardless of year while PSA seems to get tougher the "newer" the issue.