Sometimes its hard for me to follow up whats going on manga scenes, especially on fights. So I would prefer watching anime if its about figting shonen. On the other hand, I see manga as different vibe, more intimate one. I mean manga is able to deliever much stronger emotions(Jumyou wo Kaitotte Moratta. Ichinen ni Tsuki, Ichimanen de, Onanie Master Kurosawa, Watashi-tachi no Shiawase na Jikan.). But anyways, I watch anime a lot more than read manga as you basically just need to listen to, and can let yourself be distracted sometimes :D.