What are optical, coax, & AES/EBU digital I/O's?
Which is better?

Three methods for transferring data from one DAT machine to another. The AES/EBU method is the best, not only from the standpoint of cleanest delivery of data to another machine, but it will not be burdened by SCMS. The Coax is the next best method as it has lower jitter than plastic fiber optic cables (i.e. Toslink). Glass ATT type fiber optic cables & connectors do not suffer from this problem.