I have the R77-D. Love it. After one season with it the tip of it (CF) is beginning to yellow. I too debated between it and the CSONE. I opted for the R77-D, because of it's larger size, and figured the CF version would keep the can dark in colour. To me, I really like the look of the stock muffler. Firstly, its matte black finish works well with the bike's other various black bits and exposed engine. I also think the stock can's girth (short length, and 'double' height) play on the bike's muscular, beefy angles and appearance.
Perhaps someone who has heard both can chime in, but I would suspect the CSONE to be somewhere between the R77-D and the R77.