The same opinion is found in sports card grading circles. Sure, send in the Michael Jordan RC by all means, but not the 1977 Ken Clay RC?
I have just begun sending in books to CGC the past two years. I don't have any issues that are prominent "keys;" just a few first issues that brought back my youth in the 70's. However, I am endeavoring to complete a set of The Human Fly (just three more to go) and place it in the registry. i have a few books from the late 60's that I am just interested in seeing what condition is assigned to them. While I have sent in a couple of modern books, I did so for my personal collection. I will be sending in a four-issue storyline from Marvel Team-Up #41-44 that featured the Salem Witch Trials (Vision, Scarlet Witch, Doctor Doom, Moondragon). I just want to know how they grade and display them.
As most have mentioned in this thread, whatever you enjoy in the comic book hobby, enjoy.