Generally speaking, in a game of Commander, we very rarely let our Commander stay in the exile zone, because if we cant get it back again
It is entirely possible that you wont activate two of their abilities in a game
The Open is a cheaper 6 mana and easier on the White mana front, but it brings back everyone's stuff, kind of like a big fat Twilight's Call, but your deck should get more value out of it then your foe's
This works well in a few different decks, go-wide tokens like Dimir Zombies or Izzet Elementals, Azorius Spirits, or loads more
Sneak Attack Dimir Rogues Lands Wrath Naya Lands Commander Legends (November) The recent release of Commander Legends saw two more decks enter the fray
As you can pump the front or the back, you can make it high for blocking big beaters, or strong for taking out attackers