Let’s say that you’re in a stock R/U control deck (without Wildfire/Burning of Xinye) – direct damage to deal with things, countermagic, a few dragons, etc. Assume that you have no splashing going on.
Let’s assume that if you had an Izzet Signet in your deck, it’d be in your deck, but that’s pretty obvious.
However… what about the other non-obvious ideas?
Now, in a stock U/W control list, how often would you: