Manga. It's farther, doesn't have as many annoying flashbacks, doesn't have fillers, and is how Kishimoto intended the series to be.
And yes, I understand that Kakashi's Gaiden is a filler, but it's not filler in the sense that it doesn't add anything to the series. I admit the anime is cool too, because I love openings and endings, but it's getting really drawn out. Shippuuden seems to have at least one flashback per episode. ><