If an Adventure spell leaves the stack in any way other than resolving (most likely by being countered), that card won't be exiled and the spell's controller won't be able to cast it as a permanent later
In comparison, a compact combo assembled from hand may end the game with very little warning
Okay, maybe the price is a little high and requirements sometimes awkward to fulfil
If you're tempted to jam a bunch of cards like Brainstorm because you're a five-color deck, consider if any of the card-drawing Sagas are worth building around
You really have to figure out a way to pick a fight with something that won't outright kill Garruk in order to get him to transform, but that's not always possible
It pairs well with a number of backgrounds like Agent of the Iron Throne or Clan Crafter, and it provides a steady stream of mana to keep the dragons flowing