balanced outputs are superior to unbalanced outputs in that they will be totally 'noise free'.
this would be particularly useful where RCAs are susceptible to having 'noise' in the form of interference or background hiss entering the signal path.
whilst i've not tried a balanced setup, my opinion is that it has limited applications in car audio. firstly, noise is usually not an audible problem in a stereo that is well-installed and designed, and uses high quality components. this is particularly so because the distance between the 'source' (ie: HU) and amp is such a small distance.
it is however, another 'feature' that adds towards a gold standard. as such, its value may lie with your perception of its benefit. IMO, as soon as i start the engine and drive off (which is the primary reason i have a car!), the SQ benefit of such features goes out the window (or sunroof :wink: ).
it's probably also a feature that guarantees NO audible benefit, but offers a theoretical one. and perhaps its one that may solve a problem that never exists (audible noise).
more info on balanced line technical aspects can be found in the relevant tute in
basic car audio electronics (#119).
hope this helps.