Neither. Two separate entities. But eh, I'll play along.
I'll say anime. Manga is great for getting those imaginative juices flowing, seeing things play out in your mind. That's great, I really approve of that because I love reading. However, actually seeing things play out with your eyes and not just your mind, letting things envelop your senses is much better. You're not just seeing with your mind, you're seeing with your eyes, and letting the music and voices create an even wider, more profound picture.
That said, manga has a place, obviously. Manga is great, even if I don't read manga myself aside from Bleach, which is force of habit. It all depends on personal tastes, but if we look at this logically, anime should have more impact than a manga will. But this boils down to how production on both ends of the spectrum play things; how well it's done. At the end of the day, it is what it is.