Balanced vs Unbalanced Digital Cables

XLR is designed for long cable runs and noisy environments. Like concerts with tons of gear and cables. Or recording studios. I’d say it depends how your equipment is designed. If it is fully balanced internally, then, obviously, use XLR in order to avoid balanced to unbalanced conversion and back. However, if equipment is not balanced, then RCA may be better choice since why convert RCA - XLR - RCA back again? The fewer conversions, the better.

NO! Digital data transmission down an RCA SPDIF coax is a solved problem and perfectly fine. 

There are two types of IEC 60958 standard AES EBU non-optical cables:
Type I Balanced: 3-conductor, 110-ohm twisted pair cabling, XLR connectors, used in professional installations (AES3 standard).
Type II Unbalanced: 2-conductor, 75-ohm coaxial cable with RCA connectors, used in consumer audio.

In a home audio system, it won't make one bit (I feel a pun coming on)
of difference.

Best advice:
K.I.S., S.

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All else being equal, u might get an additional 3 db of gain? However, if smear is an issue, maybe go shorter rca as ribbon could get up there for long lengths. 

You have some great gear. And going balanced will make your voice exactly 3dB louder in the ongoing discussions of how digital cables make deeper zeroes and more spacious ones. Seriously, the advantages of balanced connections are very real considerations in the studio, but simply unnecessary at home. (With the one possible exception of phono carts inherent balanced output)