Good topic.
I thought sandbox was the best, but in my experience many players have difficulty to navigate the unlimited boundaries and get anxious. Many people will just do a brain freeze. In my humble opinion it take the right kind of players to do a cooperative world building with the GM.
Personally i enjoy most of the AP as long we can sandbox and go in another direction for sub-quest or do different things if we wish to do so. I would also encourage the GM to adjust the AP and make some content change based on the party composition and players to make it enjoyable for everybody.
Cheers,