Balanced outputs and Differential inputs (the technically correct name; although "Balanced inputs" is the colloquial common use) have two primary advantages and one disadvantage.
As mentioned, there is relatively little signal quality loss with "long" cable lengths. "Long" in this case meaning some number greater than between about 10 and 20 feet, where a single ended (the term for a non-balanced connection) cable will experience signal losses, starting at the high frequencies and with the starting measurable frequency rolloff decreasing as the length increases (eg maybe at 10 feet there is a slight loss beginning at 18 KHz, and maybe at 20 feet that rolloff starts at 15 KHz; just arbitrary values to illustrate the phenomena. Actual values will depend on the equipment and cable involved).
Along that long length of cable (or for that matter, a short length under the right circumstances) will be noise generating signals. Maybe the cable must run parallel to another cable carrying signal or power, for example. The longer the cable, the more opportunity to intersect or interact with a noise generating source.
With a single ended cable you will pick up all the noise sources you encounter, depending on things like how long the cable is parallel to the source, how much or what type of energy is involved, etc. There is also RF antenna pickup, which depends on the specific length of the cable run and what frequency it corresponds to. For example you would not want a cable that is 57" or so long because that makes a nice FM radio antenna. Since the spectrum of RF runs the gamut, virtually every cable length will be susceptible to some radio frequency.
With a balanced / differential cable run, it still encounters the same noise sources, and is just as susceptible to those noise sources as single ended, but there will be a cancellation when both the (+) and (-) signal cables encounter the exact same source, resulting in zero noise pickup at those sources due to cancellation effects.
Say you have a 60 Hz hum sine wave from an AC power cable ... if the (+) run and the (-) run encounter the same interference, because they are opposite polarity, it's like adding two values of opposite denomination ... +10 and -10 is zero. This works with ALL noise sources, including your RF radio pickup from the cable acting as an antenna. *
Also there is much less high frequency attenuation and what attenuation exists, happens after much longer runs (100 feet is considered a reasonable limit, and with live music in a stadium, balanced cable length is often longer than that and still works acceptably, if not perfectly).
The disadvantage of balanced cables is the higher cost of construction, and if you are a believer in cable swapping, the smaller choice of connectors and cable in the usual manufacturers' catalogs.
As for the latter, I would not personally worry much about it, but certainly there are different schools of thought on the issue. But consider even "lunatic fringe" audio manufacturers like Audio Note use standard catalog Neutrik connectors for their components; this from a company that manufactures it's own female RCAs that cost three to six times as much as a female (chassis) Neutrik connector.
As for cable, a longstanding budget cable standby are various microphone cable types from Belden, Canare, and Mogami. These are cables designed for balanced cable assemblies.
So even though the minimum cost for balanced construction cables is higher than the minimum cost for a decent single-ended equivalent, and the boutique manufacturers have some very expensive connectors in the catalog that rival any uber-fancy RCA you might find, chances are you can get by with four $5~8 Neutrik connectors and whatever length of cable you need in between. If you were building them yourself, or buy them from someone like MarkerTek (Note1) or have them built by the likes of Redco (Note2) perhaps $50 all in per stereo pair, with appropriate solder, some shrink wrap and techflex, etc.
* The astute reader might wonder why this cancellation doesn't happen with single-ended cable as well, after all, there is apparently a (+) and (-) cable there as well. The difference is in the equipment, not the cable, which is just transmitting what the equipment provides and needs. The signal with a single ended preamp and amplifier is different than with a balanced preamp and differential amplifier, allowing the cancellation effect to work with the latter and not the former.
There are the "star-quad" construction cables, designed for microphones, that do offer a cancellation effect in the cable itself with single-ended equipment. It is quite effective, but only reduces noise on each individual (+) and (-) cable, not to both together as a balanced / differential connection does.
Note1:
MarkerTek
www.markertek.com
Example: 3' premade XLR cable, Mogami cable and it looks like Switchcraft connectors (1 channel) $26
https://www.markertek.com/product/msc3xxj/mogami-mic-cable-3-pin-xlr-male-to-3-pin-xlr-female-3-foot-black
Note2
Redco
www.redco.com
Choose "custom cable"
I built a 4' one with Canare cable and Neutrik premium connectors, gold terminals, for $17.10. I can't provide a link because their interactive cable specification doesn't generate one, but there you go.
