I love swashbuckling characters, I do. But there should not be one best weapon in the game for a huge swath of characters. But right now, there is: the rapier.
If I want to make a genasi Thief of Bagdad style swashbuckler, I will be costing myself damage output (the main contribution swashbucklers bring to a party) by going with a scimitar instead of a rapier. Likewise a halfling thief with a short sword, or any other aesthetic choices that are, by the math, "wrong."
(See also no one using slings or a host of other weapons, because it's never the right decision to make.)
I'm not sure what the fix is.
Make weapon stats more similar, with only flavor between them? I believe there's an OSR game (maybe either the White or Black Hack) where every class does a set amount of damage, no matter what weapon they're using.
Make weapon stats far more complex, with every weapon being situationally good? The odds are that there will still be a "best" weapon and it'll just take the hardcore math types throwing everything into a spreadsheet to determine what it is.
What do you think? Is this a problem in your game? Have you attempted to fix it in some fashion?