Doesn’t matter.
BUT fb://page/ doesn’t work anymore, you have to use fb://profile/now. That worked for me:
fb://page/221849021186247 vs fb://profile/221849021186247 (via http://stackoverflow.com/questions/16589367/open-link-to-facebook-page-from-ios-app#comment26446038_16591116)
And if you are not sure you are using the correct ID: http://findmyfbid.com/