If both pieces were not designed with fully balanced circuitry: It's a waste of time, and you quite possibly will be subjecting your signal to extra, signal-degrading comversions/componentry(ie: differential amplifiers, phase splitters. If your interconnects aren't very long, you shouldn't be troubled by RFI/EMI, which is what balanced cables were created to combat. It can't hurt to compare single-ended and XLR interconnects, but be certain to do so at exactly the same volume levels, and with equal quality cables, so the comparison will be valid.
