Balanced vs. Single Ended Interconnects

In my system, XLR interconnects are no better at rejecting noise than RCA/single-ended cables.  In fact, they're worse.  I get a 60 cycle hum with XLRs between my preamp and amps that I don't get at all with RCAs.

All 3 of my upper end DACs are fully balanced designs.  All three sound better with XLR cables than RCA, from the same manufacturer.  Not Mogami but Grover Huffman cables (lower cost boutique).  

A balanced vs single ended cable, both being of similar CONFIGURATION, will transmit the waveform with identical defeciencies, therefore sound the same.  The balanced cable however will show a +6 dB gain over the other.  There is also some immunity to common mode noise, usually a minor consideration. 

A balanced vs single ended cable, both being of similar CONFIGURATION,

They are not the same configuration. For starters on have 3 wires and the other has 2,

will transmit the waveform with identical defeciencies, therefore sound the same.  The balanced cable however will show a +6 dB gain over the other.

Maybe SNR not gain?

  There is also some immunity to common mode noise, usually a minor consideration. 

When did CMRR become a minor consideration?

This at $25 each plus shipping?  If you get someone to order for you with an Amazon Prime account then shipping is free