I wanted to chime in with this as well.
I would label myself a card collector first, and an autograph collector second. That being said, one thing that I definitely prefer from a player, in terms of an autograph, is an early career signature.
What we see from a lot of these guys in terms of signed pieces, is their show signature. Mantle is one of the most prominent examples of this. His Show signature, is like a vintage Cadillac. It's iconic, it looks great, especially when he accompanied it with that small "No.7" inscription.
However there's something about his early career signature, that I just love and is more rare. Before he perfected his show circuit one. I've included it below.
Now chances are, short of me hitting the lottery, I'm not going to be able to afford any signed Mantle Cards. However, if money was no object, I would love to hunt his early issues of cards, with the more classic mantle signature in Ballpoint.