The fact that Sylveon has 95 base HP is a huge reason to run Sylveon over Florges in my opinion.
The difference between having 154 base SpDef and 130 isn't very important, both will be able to wall special attacks incredibly well. I feel that Sylveon can pull off a Calm Mind + Substitute or a Calm Mind + Wish set better than Florges, since it's physically bulkier. I currently run:
Florges' coverage is even worse than Sylveon's in my opinion, because having access to Grass moves doesn't really help it at all. Fairy is NVE against Poison, Steel and Fire, all of which also resist Grass. Shadow Ball at least hits a lot of pokemon for neutral damage.
And like I said, you can swap Substitute in the above set for Wish and it'd still be very good. Having so much more base HP than Florges, Wishes coming from Sylveon will be much more beneficial to your team.
Apparently Pixilate boosts Normal moves an additional 30% on top of making them Fairy-type, so it's a viable option for Sylveon once Eevee gets access to Hyper Voice this gen. Until then I think Cute Charm is just better because there is absolutely no reason to run Pixilate, other than a gimmicky, boosted Hyper Beam that will cost you the battle the turn after.
There is also the fact that Sylveon doesn't look completely awful. If you care about the designs. Florges looks like somebody threw up onto the page while trying to design a pokemon and just thought 'screw it, that will do'.