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.
Balanced vs Unbalanced Digital Cables
I have the ability to go to a balanced digital from my Lumin d1 to my SMSL D400EX. Is it worth the potential expense?