Talk:Kogitsunemaru/@comment-116.88.202.248-20150717014511/@comment-26222562-20150717102005

The basic meaning is the same... They are even written with the same kanji. Nushi might or might not imply more degree of attachment since it can also mean "spouse" whereas there's no such meaning to aruji. It's also the more archaic and less used way to read the kanji compared to aruji. Well, you get the gist.