The better HP almost offsets the difference in special defense. I can't see Florges having a meaningful niche in any tier Sylveon is allowed in. Also, with the weather nerf, plenty of Ubers will drop, specifically the Ubers that were banned because of weather, which are Thundurus, Tornadus-T, Excadrill, and Manaphy. All of these Pokemon were only broken because of their respective perma-weathers. The other Ubers not on the initial XY banlist are Landorus, Genesect, Blaziken, Deoxys-N, Deoxys-D, and Deoxys-S. Of all of these, I feel only Blaziken is clearly broken. Deo-D and S are certainly suspect worthy at the very least, while Genesect and Landorus were barely broken in Gen V and have gained new checks. For example, the now more viable Azumarill beats Landorus-I pretty easily, not to mention it walls and OHKOs Keldeo, while resisting Pursuit. (not that Tyranitar would ever stay in on it anyway) RP Genesect can now have its sweep cut short by a Talonflame Brave Bird combined with a few turns of LO recoil, while Sylveon walls Scarf Genesect without the somewhat situational Iron Head. XY will definitely have a smaller Uber tier than BW.