Competitively speaking, it's hidden ability Pixellate is better in my opinion, but if you want a defensive Sylveon, like one with Wish and Protect, then go for Cute Charm, and make it physically defensive. Any Pokemon that hits your Sylveon with a contact move, such as Take Down, and said Pokemon is the opposite gender, they may end up not being able to attack because they're in love.
But since the Attract condition isn't very common in competitive battling, with things like Swagger or Confuse Ray being much more popular, I still believe Pixelate is better, especially with Choice Scarf/Specs.