If a system is differentially balanced, then expensive XLR interconnects should not sound differently from Mogami or Gotham Cable or Canare XLR interconnects.
If components are not differentially balanced, or transformer coupled, then all bets are off.
@tvad Good to see you posting here again.
The actual issue isn't whether its differentially balanced, its whether the output of the source or preamp supports AES48 (Audio Engineering Society file 48), the balanced line standard. If it does not, the cables will affect the sound and 'all bets are off' as you put it. But transformers can do the job quite well.
Put another way, there are fully differential balanced preamps that don't support AES48 (actually quite a lot of them at this point) so they can't drive long interconnects and you hear differences when you change from one cable to another, which should not happen if the balanced line standard is being observed.
I use Mogami Neglex at home and don't worry about the 'sound' of the cables, but the equipment in my system supports AES48.