In my opinion, it’s MF. Going into Marineford, I never cared much for Ace, and it didn’t help that Ace didn’t receive a lot of his characterization until after MF when we got Luffy’s flashback. Looking back on Marineford, almost all the fights were disappointing. Vista vs Mihawk, Jozu vs Aokiji, Marco vs Kizaru, and WB vs Akainu round 1 were all almost completely off paneled. Blackbeard vs Sengoku was offpaneled. The other Divison Commanders didn’t get to do anything except show off their ability in a panel or two against fodders. Jinbe only fought an incredibly easy to beat Moriah. Hancock only fought fodders. Doflamingo got to ambush Jozu once and then fight Crooodile off panel. Luffy was either beating up fodders or getting tossed around by people much stronger than him. However, Whitebeard was easily the best part of the arc, and his death was really epic. Ultimately, MF was just a glorified hypefest, which never got any fleshed-out fights, even though Oda teased some cool fights. It has very little replay value because of this imo.