Originally Posted by JBord

I had never really thought about it, but this is a perfect description for the difference.

I suspect the reason purists preferred stirred is that you can really taste the liquor, which is more difficult when it's near freezing. Considering that the original martini was gin, and the only correct martini in the UK is gin, shaking a martini so that it's ice cold would hide the gin. That's why James Bond had an odd order - why would a Brit hide the gin ? With the newer vodka martini, shaken makes a lot more sense, as vodka is so often served chilled or even ice cold.