@m_j_s
Correct. The question is SP/DIF (unbalanced) vs AES (balanced) digital cables and not the analog equivalent that provides a volume boost.
On my Aurrender W20SE to Audio Research Reference CD9 SE DAC the AES sounds a slightly better. That is probably what Lumin will say. I would follow their guidance. But typically the quality of the interconnect will improve the sound quality vastly more than the connection type for high quality components. For low quality components it is harder to generalize.