This is why XLR is especially good for long runs. The additional line for the single path is also responsible for the 6 dB gain
If your setup supports the balanced standard there will be no 6dB gain difference between balanced and single-ended.
I'd not considered this point before, but given that the signal is duplicated then reversed then transported then recombined, doesn't that mean that any coloration or other effect by the interconnect is simply negated? So, you don't really need fancy balanced cables?
If your equipment supports the balanced standard then you don't need fancy cables. If it does not support the standard, you'll find yourself auditioning cables to find the one that sounds 'right'. Personally I find this a bit silly, since the balanced line system is a technology that eliminates cable colorations.