Below are the main features which you will not find in MAX9259/60 –
MAX9275/ MAX9276 can send data through coax and STP both while in MAX9259/MAX9260 only STP link is possible.
MAX9275/ MAX9276 have added “High Bandwidth Mode” which MAX9259/MAX9260 does not have.
MAX9275/ MAX9276 have “High Immunity Mode (HIM)” which is used for reliable transfer of I2C data. MAX9259/MAX9260 does not have HIM.
MAX9275/ MAX9276 support UART-UART, UART-I2C,I2C-I2C communication whereas MAX9259/MAX9260 supports only UART-UART, UART-I2C communication.