Somehow, I tend to think that cleats of the same mass, in the same places, are going to sound the same. Call me crazy.
That said, from my perspective diamonds are going to: a) give you more crack-coverage for your given cleat mass, and b) anything that avoids putting things parallel to the grain sounds like a good idea to me.
Wayne - maybe it is just a matter of the instrument in question? Are diamond cleats
lipstick on a pig if we're talking about a cheap factory bass?