Ralph knows his stuff, BUT, 'my' personal experience running 100% true differentially balanced systems is that "I" have heard the difference between 0.5M XLRs and 1.0M XLRs from the SAME company: Eichmann Express Copper. Now that was ~ 10 years ago but I never tried it with other XLR cables
Hopefully R will chime in
Hopefully R will chime in