i actually think josh would 100% win because his NORMAL singing voice is actually pretty deep

panther has an impressively awesome range including his deep tone but it's kinda like a thing that he uses on occasion (for example when he's singing as thomas light he sings deeper) rather than josh using his deep voice all the time PLUS I feel like panther's deep voice is more like a seductively low tone that makes everyone scream which tbf josh could do too but its different with him

josh is better with his deeper range so I think he definitely holds that over the protomen if it were real my bets are on josh