Adobe has lots of "features" that something like Sumatra doesn't, but Sumatra has a minuscule footprint and opens pdf. files quickly and cleanly - been using it for a few years and had another free one that was similar for years before that. Never had reason for anything else.
Of course, I also use VLC for most movie files and have an older version of Winamp for music files (5.581) and used to have Winamp 2.81 for years before that - simple can be better in my book.