Hi Guys,
So far I’ve only used Game Center and Google Play in my games for leader boards etc. I’m considering trying out Facebook.
I was wondering if anyone here had used it? Or what methods you prefer to use for player to share scores/complete with each other?
Thanks 
native is best
Like @energyy said native seems to get the most engagement so we would recommend sticking with native but adding extra/other Facebook/social features on top such as sharing.
That depends on what you want to achieve.
If you want to separate the platforms and don’t care to implement it twice, you might want to use the native frameworks.
If you want to provide cross-platform gaming and sharing, you might want to use third party frameworks, which provide their own leader boards and sharing mechanisms or other social features like quests and what not. Some offer the functionality for free, other come with a cost. Those, which are not free provide everything you will ever need. From IAP, to social, to multi-player.
It’s a matter of your needs, integration time and your pockets.