Admittedly, 9 vs 9 does fit very well.
But:
1. The Strawhats force is larger than just the 9 Strawhats:
- Lucci
- Kaku
- Stussy
- Bonney
- Sentomaru
- The other satellites (?)
2. The 9 Strawhats aren't the strongest characters on the Strawhats' side.
The three CP-0 agents seem stronger than all Strawhats bar the monster quartet.
And if the CP-0 agents betray them, they again become enemies for the Strawhats (with superior portrayal to the 9 VAs).
But it doesn't seem like they intend to do so.
3. The 9 Vice Admirals aren't the strongest on the Navy/WG's side:
- S-Hawk
- S-Bear
- S-Snake
- S-Shark
- Any other Seraphim Saturn brought along
With Saturn at Egg Head, he'll presumably regain control of the Seraphim.
The 4 Seraphim are stronger than the majority of the 9 VAs, and plausibly all of them.
Furthermore, these Seraphim are way, way, more hyped and relevant to the story than the 9 VAs.
It is for these Seraphim that the Shichibukai were disbanded. And the Shichibukai have always been given far superior portrayal to VAs (Doflamingo's debut was literally toying with VAs).
There's a real sense in which the Seraphim are the "main antagonists" of Egghead moreso than the 9 VAs.
The 9 VAs aren't necessarily the calamities + Tobi Roppo of Egg Head. At least their current portrayal doesn't support it. If anything most of them seem to be more like the Numbers.
The Seraphim have portrayal closer to that of the Tobi Roppo.
They've been given the highlighted focus, clashed with the strongest members of the Strawhats etc.
9 VAs vs 9 Strawhats ignores the elephant in the room that is the 4+ Seraphim.
Cc:
@Paperchampion23,
@Sir Yasheen,
@Elder Lee Hung,
@MarineHQ,
@SakazOuki,
@LANJI CUCKSMOKE.