Differential Balanced Sound Quality

You’ll find the thoughts on this very polarizing, and in reality, it just depends. My current system is all single ended, with the exception of my phono pre out. I run that balanced for several reasons. I’m not a fan of preamp to amp balanced connections. I’ve always preferred single ended overall. YMMV

     My preamp, amps and universal disc player offer both balanced and unbalanced connections.  I use balanced/xlr cables for all connections since they are objectively more secure and I subjectively perceive them as quieter and a heck of a lot cooler than unbalanced/rca cables.  My dog and 2 cats also can't knock anything loose when they manage to get back there and start messing around.

Tim 

Have had both and I must say that while the balanced front end was not of the quality that my present unbalanced front end now exhibits, there existed a depth in the music that was at times uncanny. Reducing the noise floor in my opinion is a critical aspect of a system when attempting to hear into the music. 
I still use balanced power with both an EQUI=TECH wall unit and Balanced Power Technologies  AC treatment. Still I have found that "spooky" sound quality a bit less prevalent in the current system. 
Using a BAT VK P 10SE phono stage fed my system a very deep and quiet signal. Alas the unit at 20 years old began to have problems. 
Running high efficiency speakers brings out the charm of a balanced system. I say it's worth it.

@dentdog Do note that the technology that makes power "balanced" is different from the technology that makes amplification equipment (i.e., sources, preamps, and amplifiers) balanced. 

If you care for an explanation, read on. 

Apologies for length, but I'm just now starting to understand all this and wanted an excuse to type it out so that I could consolidate the learning.  Please do offer corrections anyone...

--Balanced Power--

Traditionally, AC power is delivered with 120v on the "hot" line and 0v on the neutral return.  In balanced power equipment, the hot line is run at +60v and the neutral is run at -60v.  

--Balanced/Differential Equipment--

Alternatively, the balanced equipment discussed above separately amplifies the positive and negative parts of the electrical signal.  This requires double the circuitry because you have to amplify two signals (0-to-positive and 0-to-negative) instead of one (negative-to-positive) as in single-ended equipment.   If you imagine music as a sign wave, then balanced equipment is separately amplifying the upper and lower halves of the wave.  The benefit of this added complexity is that any noise introduced into the signal by your equipment will be cancelled out when these two "half" signals are re-combined to make the full-wave signal that drives your speakers. This is because any injected noise will appear positive going in one amplification circuit and negative going in the other... add them together and you get automatic noise-rejection because they'll be in exact opposition. 

--Distortion & Preferences for Balanced vs Single Ended Equipment--

Interestingly, in addition to external noise sources, every amplification circuit also creates its own "ringing distortion." If, for example, you play a sign wave at 1000Hz, the circuit will also produce a signal of reduced amplitude at different harmonics. Thus, you'll see small spikes at 2000Hz, 3000Hz, 4000Hz, 9000Hz, etc. These are called even (2000, 4000, etc.) and odd harmonics (3000, 9000, etc.). The balanced circuitry also eliminates all even harmonics when the signal is combined to re-create the music. This is because their peaks line up directly with the peaks of the original signal and they get cancelled just like any other noise/distortion that affects both the positive and negative amplification circuits at the same time.  

While this is a good thing in principle because your music has less distortion, about 1/3rd of human ears actually find the second harmonic distortion pleasing.  It seems that this harmonic ringing creates the perception of increased warmth and 3-dimensionality in stereo listening.  Alternatively, signals with a dominance of 3rd harmonic ringing is often perceived to have increased clarity and detail... and again is preferred by about 1/3 of listeners.  For more discussion from Nelson Pass, read this link:  https://positive-feedback.com/audio-discourse/the-pass-h2-harmonic-generator/

I believe that variances in preference for these different distortion profiles is likely one reason why you see such different (and strongly held) recommendations about the importance of balanced vs. single-ended gear from different posters. 

While my training as a scientist initially biased me towards a "balanced is better" perspective (why wouldn't you want less distortion???), I have subsequently found that I have a consistent preference for gear with a 2nd harmonic dominant profile.  At this point I'm confident enough in that preference that I'll only buy single-ended gear.  

Sorry for all the typing folks.  I'm bored.  Thanks.