This is one of those threads that can go on forever as there is no real answer. As has been pointed out it is system dependent. There is little or no agreement among the most experienced designers and reviewers. Martin Colloms, who has tested about everything for 30 years has said that 95% of the components he tests sound better single ended and that balanced best use is in long runs in studios. BUT, he uses VERY expensive ICs. A recent article by a recording industry professional in HIFICRITIC mag. , which Colloms publishes, came down on the other side. The author maintained that equal results could be obtained with much cheaper cable with balanced. At the same time he pointed out, as mentioned above, that not all "balanced" are created equal and that standards about how it is implemented are very imprecise, a situation not unknown in other area of audio. He also recommends transformers in some cases. He notes that balanced seems to be popular in US and Japan but not Europe, which he finds strange. So the answer seems to be dependent on each system and user, another not unusual finding.
