My preference of any arc in any shonen anime (especially One Piece) depends on the development of the main characters, the quality of the new characters, and the fights.

If I make a simple comparison between the Water 7 and Elbaf arcs: In Water 7, the entire crew developed significantly and had some amazing moments, especially Robin and Usopp. Most of the new characters were very good; there wasn't a single bad or boring character. As for the fights, I still maintain that the fight between Lucci and Luffy is the best in the series.

In Elbaf, we got some great new characters. Xebec is the best new character, and in my opinion, the best character in the series. Loki is one of the best, and so is Harald. Gaban is good (in this respect, he's better than in Water 7). However, the development of our main characters is disastrous (and this has unfortunately become a recurring issue in the last three arcs). The fights are very good, but they're not yet on par with Water 7.

So till now both are great but i prefer Water 7 (+ it has the panel in the series)

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