I prefer to find the earliest example of a persons sig that I can find and I have a bias that leans heavily toward fountain pen signatures. At times I will upgrade for exactly this reason.
That being said, as Mike already stated, sometimes the later example of a player's script may be the only version you can find. In this case, I would be more than happy to add it to my collection if it filled a hole.
BTW, regarding Bullet Joe Bush. Here are a few examples of his signatures through the years. A signed photo of Bullet Joe probably signed in the early- mid 1960's. A typical later example of his signature on a 3 x 5, circa 1970. An unusual signed check whith his given name Leslie Ambrose Bush. Finally, an earlier example of his signature, circa 1953, on a GPC in fountain pen where his script doesn't show the typical shakiness that you see so often. This example is far more challenging to find, FWIW...