Collectionview or Scrollview or PageViewController, Which one is most preferable?

It depends on requirement. If too many pages or items, then Collectionview or pageviewcontroller is good option. Because Collectionview can reuse cell for display view, whereas PageViewController load only current page,previous page and next page in memory. As Scrollview loads all subviews in memory, it will consume too much memory.

Pageviewcontroller load multiple viewcontroller in memory. So preferable most in following order :

1. UICollectionview

2. UIPageViewController

3. UIScrollView