Nucleus Plus audio: HDMI or USB?

All other things being equal, is there any reason to prefer USB audio over HDMI audio from a NucleusPlus?

In my case, it’s connected to a Lyngdorf MP-50. The MP-50 only plays network audio via AirPlay, so higher resolution files are downsampled if I use the network connection (Lyngdorf’s TDAI product is a Roon endpoint, but sadly not the MP-50).

I’ve tried listening to both USB and HDMI with a few songs, but can’t detect any meaningful difference (but I’m not sure that I really would anyway). On one hand, the (possibly wrong) Lyngdorf specs slightly favor USB over HDMI (192kHz/32-bit vs 192kHz/24-bit maximums). On the other hand, it would be more work to permanently install a USB cable between two cabinets for me, and I already have an HDMI cable installed and working happily.

I can’t find anything in the Nucleus specs or forums here that suggest a general preference (USB or HDMI) for the Nucleus box. Is there any hardware preference?

HDMI would normally be preferred for multichannel use, or as in your case where it is simply easier to employ. If you use AirPlay you aren’t losing out anywhere. Either input performs to the exact same limitations.