Narratively speaking (ik it's hard for Onepiss fans to understand narrative which is why they think this story is good
), Akainu should be a better leader. Maybe not a better tactician since he's more of a fighter himself than one who'd oversee a war but definitely a better leader overall. The navy is verbatim stated to have gotten stronger under his leadership which is quite literally the only criteria that
should matter when judging leadership. Yeah, unity matters but there's no proof that the marines have gotten less united, in fact since Akainu is more extreme, the navy should only get more united.
Anyways, as I was saying, why should Akainu
narratively be a better leader? Well simply put, every generation surpasses the generation that preceded it and the targets of the new gen will be the middle gen since middle gen has the control of the status quo right now and will all be the important fighters in the final war. Not. The. Washed. Old. Gen. They're done with the story, they only exist to tell the history and give context to why the OP world is at is it.
Roger/Whitebeard have been surpassed by Shanks/Mihawk who will be surpassed by Luffy/Zoro. The same way Garp/Sengoku have been surpassed by Akainu who will eventually be surpassed by Koby.
SIMPLE NARRATIVE.