It's actually not that simple. Replica flowen's is far stronger than nearly all fake flowen models besides the real one, and is technically stronger if you have the set bonus.
Real Flowens 300-320atp 85grind 34ata, 490 total atp
3079 Flowen 290-300at 9grind, 25ata, 318 total atp
Rep Flowens 230-300atp 21grind 28ata, 342 total atp
Set Flowens ??? -450atp, 342 x 1.5 = 513 total atp
If minATP is affected equally, then 408-513 total ATP for replica with set, averaging 460atp, whereas real flowens is 480 average, so it's relatively close but replica can hit higher potentially. Similarly, this is true of replica and 3079(second best model) as well, with the 3079 averaging 308atp and replica averaging 307atp, with replica having a larger variable and potentially higher numbers. This is also combined with the fact that you can put charge on replica instead of spirit, allowing use on more hunters and less costly overall (spirit is fluid heavy and becomes unusable below 11 tp). It does however have 6 less ata than the real one and 3 more than the 3079, though it's far more than the other models which have 5, 7, 9, 12, 13, 15, 17, and 19 ata only.
As for the DB's sabers, the replica is stronger than most but there is one replica that is comparably strong to it without set, the 3064 model. The ata across the different models is also much better overall (ranging 21, 27, 29, 29, 30, 34, 40, and 48) than with the flowen's which have abysmally low on most of them.
DB 3075 300-340atp, 85grind, 40ata, 510 total atp, average 490
DB 3064 289-301atp, 18grind, 48ata, 337 total atp, average 331
DB Saber 200-250atp, 44grind, 43ata 338 total atp, average 313
DB Set ???-375atp, 338 x 1.5 = 507 total atp, average 482
None of the db's weapons have a special on them though, so there is no potential advantage like with flowens. The atp variables are the basically the same for 3075 and replica, and the replica also has more ata than the 3075 by 3 (but falls short of the 2nd best model by 5) so technically the replica with the set has the arguable overall advantage here, as the variable and max atp differences are negligibly small.
With both DB's and Flowen's weapons, the 9star replica isn't a bad option overall. They are on par with the 2nd best model without the set, and with the set are raised to be comparable to the best models. They also can be acquired at earlier difficulties and have lower requirements, so they can be used much quicker.
If I could do set bonus changes, I would definitely want to extend at least DB's set to include the 3075 model (and create new item sets too). However, I would be hesitant to extend db's set bonus to Zanba (the weapon that the actual DB wields in game when you fight alongside him), and the same goes for Flowen's bonus and the respective 3084, as those swords are already arguably the strongest swords in the game by a wide margin with their sacrificial specials.