Digital RCA vs AES/EBU connections

If both the transport and DAC have RCA and AES/EBU connections, and assuming comparable quality cables are used for the 2, how would the sound differ? Which would you prefer? Thanks
I've made a few comparisons like this, and even though my eyes & brain prefer the aes/ebu standard connection, the rca imho sounded better in most cases.
I have always found digital AES/EBU connections to sound relatively thin in the midrange. I have also found that using BNC or true 75 ohm RCA connectors is a significant upgrade if you use the coax connection.
I have not made comparisons, but I know that Forsell prefers its bnc connector, even using RCAs with their supplied adaptor, to AES/EBU, and that when I upgraded my Audio Logic dac and asked them to add another RCA jack for my 24/96 transport, after discussing it with them I had them replace the AES/EBU connection with the new RCA, because I was told that, properly implemented, it is a better digital connection than AES/EBU. I also recall Gene Pope of Pope Music telling us at an NJ Audio Society meeting that he felt the AES/EBU connection was an inferior one (although he felt that the S/DIF interface was clearly superior to all others). Given all this, it might be a good idea to see what the manufacturer(s) of the equipment you're using recommend; it could be that they have optimized their unit for a particular connection.
These are all very interesting responses. Hopefully mine, although not in agreement will offer some, will offer additional insight. I started with MIT T3 RCA cable from CAL Alpha/Delta. Replaced with XLO 4.1 w/AES-EBU connector. Dramatic improvement. Borrowed HT Cyberlink copper w/RCA and compared to XLO. Like XLO better. Cable or interface? Can't decide. Now have NBS Mine/Serpent w/AES-EBU. Very satisfied. Smoother than XLO, but not more detailed. Again, cable or interface. Many cable manufacturers will say AES/EBU is better connection. Let you ears be your guide.
It's been a long time since I've looked at the specs, but I believe that AES/EBU has more bandwidth. I did tests several years ago showing much greater signal loss on HF (Above 8k) with coax
It would seem to be difficult to compare an AES/EBU cable of one brand with a RCA cable of another as the cable colorations would affect your judgement. I have also found that where certain cables "lock in" to a situation, that anything you try to compare them to will sound inferior. I have only had the opportunity to compare the Apogee Wyde Eye AES/EBU to its RCA counterpart. The differences were very subtle. The AES/EBU seemed to have a little more detail but the RCA cable seemed a little smoother. I would not be surprised if others would hear different with different equipment or even different cd's. I think the construction of the cable and the characteristics of the associated equipment matter more than whether you use AES/EBU or RCA or even toslink, for that matter. With digital cables, the characteristics of the connectors would also be very important. I have a situation in one of my systems where the lowly Monster Lightspeed 100 has either beat out or equaled all comers so far including a $250 Madrigal. Only the HT copper has been a little better. I have tried the XLO and HT cables mentioned above on my Parasound CBT2000 and preferred the the HT. However, when comparing the same cables going from an Audio Alchemy DTI 2.0 to a Micromega dac and I preferred the XLO.
It needs to be pointed out that some components have balanced outputs but DO NOT have fully balanced circuitry. And in this case may actually degrade sound if XLRs are used. Components with fully balanced circuitry are more expensive, and the only way to know for sure if the component is fully balanced is to contact the manufacturer. That said, Sonic Frontiers strongly recommends using the balanced outputs of their fully balanced Line series of pre-amps and Power series amps. I have their Line 2 pre-amp but haven't tried XLRs yet, but intend to, as all my components are fully balanced. One reason (maybe?) to prefer XLR is that they provide a more positive connection, ie I have some high quality RCA ICs that are a little loose,-- and no way to tighten them. A Synergistic Research Tech. Rep. said he personally preferred RCA interconnects for its (perceived) slightly fuller, richer sound, BUT he also said that among his collegues he was probably out voted by those who preferred balanced. Like everything else in this weird hobby, you just have to try it and see which you prefer. That's what I intend to do. Cheers. Craig.
Garfish's explaination is correct but not for digital connects only analog. The AES/EBU looks like a balanced interconnect but the AES/EBU receiver chips have not similarity to the balanced circuitry on the analoge side. AES/EBU shares the common mode rejection but that's about all with balanced. AES/EBU has a higher bandwidth then digital coax or optical and from an engineering perspective is superior. If a Coax cable sounds better its because the AES/EBU implementation is flawed on the particular pair of components. Also AES/EBU cables are more likely to sound similar (ie from cheap to expensive) because the engineering has more margin on bandwidth.
Keis wrote "Garfish's explaination is correct but not for digital connects only analog" Maybe he's from Florida and didn't read the posting correctly :-)
Garfield. I know from experience that the Sonic Frontiers preamps are significantly better when using balanced out - this is because they have better dynamics this way - it has little to do with the bal vs unbal debate, just the way the SF gear is designed. You may be in for a treat.