To be honest, it really depends for me. I don't really prefer one medium over the other. I'll pretty much watch any anime and read any manga that isn't hentai. However, if a manga I'm reading has an anime announced, I'll usually switch over to the anime instead, which is what I did w/BNHA originally and Ancient Magnus Bride.
What I don't really like is when an anime comes out from a manga I already read, I know what's going to happen since I read it in the manga. For example, I know what's going to happen in One Punch Man season two when it comes out, since I read and am caught up to the manga.
However, for stuff like Once Piece and Case Closed, I really don't have time to watch over 800+ episodes of a series I already started reading. So, for stuff like that, I strictly stick to the manga version.
Also, I never really care for light novels outside of the Kagerou Project novels and Durarara!!, Didn't plan to say anything about LNs since the op didn't mention anything regarding them....