Hmm,
It's late at night, and I can't verify that I read every word of every post above, so apologies if I missed someone else pointing this out, but the dimensions of the stylus is nearly irrelevant. Only the tip of the stylus enters the groove. See my systems page for a real close-up of the stylus in the groove. I believe the photo was taken with an electron microscope. Someone may correct me on that though. You can't even see the entire stylus, but you can clearly see the groove walls, and only a tiny portion of the stylus riding in the walls. So, shape is a factor in the contact patch, but it's the tip of that shape that handles the information retrieval.
Yes, it could be effectively argued that the dimensions of the diamond color the sound that would be transmitted to the cantilever, but how much of a factor this would be compared to all of the other influences that shape a cartridges sound, I think might be negligible? Then again, as audiophiles, it's difficult for us to find anything negligible. Even the room temperature is a factor.
Cheers,
David