Given that the system does not have significant ground-loop noise, the coax interface will outperform the Toslink, If you use a decent coax cable that is. The Optical conversions add jitter. If the system has a lot of ground-loop noise, the Toslink will be better simply because it breaks the ground loop.
I2S is the native interface to most D/A chips. Because there is no need to encode the clock and data into a single signal, this makes it superior technically to S/PDIF coax. Termination and handling of the transmission-lines of I2S is non-trivial however and many of the early implementations were not very good. I2S consists of 4 signal lines: MCLK, SDATA, L/RCLK and SCLK (aka BITCLK). The HDMI connector used with the differential version of I2S was chosen by PSAudio and adopted by Wyred 4 Sound and Empirical Audio, who also uses RJ-45. I2S has been used in single ended version with DIN and RJ-45 connectors for about 10 years. The earliest was Audio Alchemy. Differential version has 8 signal lines and ground. Single ended has 4 signal lines and 4 return lines (grounds).
Steve N.
Empirical Audio
I2S is the native interface to most D/A chips. Because there is no need to encode the clock and data into a single signal, this makes it superior technically to S/PDIF coax. Termination and handling of the transmission-lines of I2S is non-trivial however and many of the early implementations were not very good. I2S consists of 4 signal lines: MCLK, SDATA, L/RCLK and SCLK (aka BITCLK). The HDMI connector used with the differential version of I2S was chosen by PSAudio and adopted by Wyred 4 Sound and Empirical Audio, who also uses RJ-45. I2S has been used in single ended version with DIN and RJ-45 connectors for about 10 years. The earliest was Audio Alchemy. Differential version has 8 signal lines and ground. Single ended has 4 signal lines and 4 return lines (grounds).
Steve N.
Empirical Audio