I agree with those guys. With a few exceptions, I don't think signatures add much monetary value over an equally graded blue label book. Do whatever will make you happy when you look at the book. I am having Neal sign a Batman #217 NM and a Batman #251 CGC 9.0 at Baltimore next weekend. I didn't already own the books, but #217 is the issue that was out when I was born and #251 is my favorite comic book cover, so I bought the best grades I could afford. For me, I will end up paying more to have him sign it and submit them to CGC SS than it will add value to the book, so I'm strictly doing this for personal pleasure.
I used to get celebrity autographs at comic cons on the 8x10 photos they have at their tables. About a year ago I started having them sign an appropriate comic that they were involved in and submitting it CGC SS. That way I get their signature, it's witnessed, and it's on a media that will hold or increase in value.