The biggest risk is treating one sealed box as a rational way to hit one exact card
Getting three or four spiders each time you cast the card isnt hard, and its a must in spider typal decks
These effects are so much better when they give you a way to clear lands off your library, and this case gives you up to two land drops off the top each turn
Ophiomancer's ability checks if you control a Snake at the beginning of each upkeep
It does not, for example, change when you may activate abilities that can be activated "only as a sorcery." (6/16/2023) Gandalf the White affects a permanent's own enters-the-battlefield and leaves-the-battlefield triggered abilities as well as other triggered abilities that trigger when that permanent enters or leaves the battlefield
As such, as a new Commander player, I would probably value the lands from Open Hostility more than the lands from Stalwart Unity, even though the Stalwart Unity lands have slightly more value