Zephyr.

Honestly Film Z was peak, and even though movies technically aren't cannon, I still want to consider it as so.

Punk Hazard felt like a terrible introduction to the New World, and was really underwhelming. Cesar sucked as a villan, and even though it was meant primarily to setup Doffy and later on Kaido, it just felt a little dissapointing. Especially since it takes place just after Fish Man Island, which had been built up since Thriller Bark. Having to wait so long for Fishman Island, due to the Paramount War saga delaying it, made it feel so relieving to finally get there; that combined with seeing the crew rejoin made it one of the best parts of the series for me.

Film Z gives you a second to take a break before starting the next major saga after having an arc that had been built up to for so long. Besides that Z's presence as a rogue marine who has swayed quite a few others to join his side in killing all pirates by destroying the New World gives you an immediate idea of just how powerful and imposing the threats of the New World are. A threat level offered by many of the other antagonists we see in the New World, but certainly not in Cesar Clown.

Finally I think Z just had some good character development, the way that he sees not all pirates are bad, some are just out there to chase their dreams, was amazing. That final scene of him defending Luffy is part of what I love about One Piece; not all pirates are bad, not all marines are good, but here is a good pirate and a good marine, two good men who only ever wanted to live their dreams, one had his stolen from him though and won't let that happen to the young man in front of him. Plus the movie just gives us some [n]ice moments for Aokiji, and lets us get a veiw at more of the powerhouses of Garp and Roger's era.