What I did when I introduced my very non-technical partner to a mac was leave it at "natural" scrolling, show her the two-finger scroll gesture, let her try it out, then I turned off natural scrolling and asked her which she liked better. She picked the latter hands down. I knew there's a reason I'm with her :)

It's totally a matter of personal taste, both are objectively right depending on what one thinks the thing being manipulated is.