I don't know if they still use the same slogans, but about 10 years ago I saw an ad for Masters and Triangle chalks. Under the Masters the slogan was "Stressing Smoothness", and the slogan under Triangle was "Stressing Firmness". I spent a few weeks carrying around both types of chalk, using the Masters for normal shots and the Triangle when I needed to get extra spin.
Eventually it just got to be too much trouble to be constantly switching chalks. There was a real difference though - especially when drawing a mudball on old felt.
Another thing about this is that it really drove my roommate crazy. He couldn't figure out how I kept beating him when I was "obviously" warped.
There was a short story in either BD or P&B about that same time about a guy who's given different colored chalks for different shots, and ends up being the world's best player because of it. I'd love to see a reprint of that story someday.
