Balanced operation properly executed is bound to be marginally quieter than SE operation, all other things being equal, because of Common Mode Rejection, if for no other reason. That difference may or may not be audible if SE operation is already very quiet. So your single experience does not amount to a definitive judgement. For one example, did you re-wire the connection from cartridge to phono input before comparing balanced to unbalanced mode? Was the balanced mode achieved using the optional XLR inputs of your PhonoBox? I can and do live with SE phono in one system and in balanced phono in my other system. But if balanced is readily available, I would advocate for using it. Just saying. It costs practically nothing if the phono stage offers balanced operation.
McIntosh MT5 tonearm swap out?
Has anyone swapped out the tonearm on a MT5? I would love to see if it's possible to do replacing it with a 5 pin balanced tonearm.