Since both things have their own advantages I love both equally. The Manga is great because it doesnÂ´t have fillerÂ´s that distract you from the main story arc. On the other hand some fillers in the anime help adding a little depth. Best example is SmokerÂ´s flashback in Loguetown where we saw him witnessing Gold Rogers execution. I see Gold Roger totally different then I did it before in the Manga thanks to this episode.
Another advantage of the Manga is that you can consuming the story in your own pace while you canÂ´t do that with a TV episode. The anime on the other hand has great voice actorÂ´s (NOTE: IÂ´ve never seen the english version so far) that fit the characters well and add a lot more personality to them.
The Manga is B&W what often is a quite good thing because lots of the environments look bigger then they do when we see them in the colored anime. Then again the colors are also an advantage of the anime because the Cherry Blossom Mountain looks just so awesome in colors that the Manga counterpart canÂ´t compare to it.
The Anime also has a soundtrack, what is a great thing to support a story.
And a last silly aspect is that it is a lot easier to own One Piece if you pick up the Manga. If you have all issues you can be sure to have nothing missing whereas if I burn every episode that airs over here it will still be the incomplete cut version.
Well just as I said above I like both equally. And do not think that the one disturbs the other with itÂ´s coexistance but that one supports the other. :D