Whats type of digital cable is better?

att glass optical woud be best, toslink is inferior to rca, but the att interface adds $400 to most transports and processors WHEN they are avail such as on wadia etc.

Personally I prefer the AT&T (or even better, the S type glass). By comparison the coax and balanced connections sound dirty (but one man's dirt may be another's ambience). Certainly, AT&T enjoys far greater bandwidth than coax and XLR and so should produce a square wave with sharper corners etc. But there is always some danger in such general rules. From experience, it depends on what the maker of your gear has thrown the most money at. If the maker recommends say XLR, then this is probably because she/he has put more effort into the performance of this output/input. And yes there are differences. I once compared the use of a Meridian 500 transport with using the Meridian 508 as a transport. The performance of the 500 was vastly superior, and I asked Meridian why. The answer was simple - since they expected the 500 to be used as a transport (and not the 508) they had put a much better output module on the 500.

I concur with Redkiwi. The best interface is the I2S interface, however. I enjoy my all in one player, so I don't have to worry about this at present.

This depends on what you're using it with. In most cases, we find AES/EBU works best. This varies. An exmple would be WADIA. With WADIA, we have never found anything to sound better than ATT. With Muse gear (w/o the I3W3 in/outs) we find AES/EBU is always the hands down winner (with I3W3 AES/EBU does not compare). On the bel canto digital, Tos link sounds best (and this is very unusual, but explainable). I3W3 (the latest version of I2S) is the best choice, but not available on most digital components.