For the same price, we offer both unbalanced and balanced versions of our analog interconnects.
First, the bottom line: When a component gives you the the option of connecting balanced or unbalanced the sound in all cases (we and our customers have so far) tested (certainly, not an exhaustive study, but very highly respected components e.g., D'Agostino Momentum amps) was better unbalanced.
The theoretical and engineering attraction of balanced topologies is that they suppress even order, especially second order, distortion products. That's a good thing*. Balanced topologies also are less likely to produce hum when there are ground loops. Also a good thing, especially if you run a recording studio.
So why does the unbalanced mode, when both are available, sound better than balanced? My experience as a radio frequency (rf) engineer suggests that what is probably going on in audio and rf are similar. But, in rf, the harmonic and intermodulation distortion are actually meaningful because these distortion products can degrade communication links. The case for audio is a little more complex and somewhat contradictory.
In audio, harmonic and intermodulation distortion (of low order) are built-into our hearing mechanisms. Our ears are mini speakers in that they produce intermod and harmonic distortion products when sound enters our ears. (Our ear doctors measure these distortion products as a test of hearing quality). So a little low order distortion in our music is not terribly harmful to our enjoyment of the music since our own ears are contributing a little of their own distortion to the music.. But as the distortion products become more complex and of higher order (say 7th, 11th, 23rd or 121st order products) they become more disconnected from our hearing mechanisms and the music and, as you might expect, annoy us
When we characterized linear rf high power amplifier topologies for their distortion performance and found that balanced topologies did have the lowest second harmonic distortion products but their higher order distortion was worse than their unbalanced counterparts. i think audio and rf amps share a similar quality (albeit for different reasons) in that higher order distortion products are more harmful to the mission than lower order products.
Now for some techtalk. In ideal balanced topologies, say a push-pull amplifier, identical active and passive components work together so that they cancel undesired even harmonic products while at the same time adding the desired signals. If both halves of the push-pull circuit are identical this works,
But, in the real world, no two components are identical and in the push -pull process the extra non-ideal components needed to satisfy the balanced topology add and increase the higher order distortion products instead of cancelling them. Unbalanced topologies can do the job with fewer components.
Balanced vs Unbalanced ----- which is better?
* you would think. However, several designers are purposely adding 2nd or 3rd order harmonic distortion to their amp designs because they say their customers, and they, like the sound better with distortion.
"...nothing gets you closer to the music."