both are techniques used by mortals whose abilities overlap in several aspects, such as the "armored elephant path" cultivated by croocked soul, where would the difference be between them?
In RJMI martial artists only have the strength of very strong mortals.
Peak Body Refiners can have strength up to Nascent Soul cultivation - body refiner are only seen in middle realms like Spirit Realm.
Both only have mortal lifespans (up to 100 years).
What do you think?