I know that peak-peak voltages of an AES signal are much higher than peak-peak voltages of S/PDIF signal. something like 5V compared to 0.5V (but I think there is a range of acceptable voltages for each specification, I think AES is 3V-7V peak-peak, not exactly sure though, someone please correct me if I'm wrong.)
however, I'm not sure about the 110 ohm vs. 75 ohm question..