Debating this for my izzet deck. {thought scour} or {inaction whatever} for card draw?
The detain one. Milling may help your opponent just the same as hurting, while detaining creatures can be an effective tool. Most decks use creatures to win one way or another.
I personally would only use the Detain card if I was creature heavy. If your only creature is Snapcaster I'd go the CMC 1 card because detain is generally only worth it if you have plenty of creatures to attack with
If you could please ask these questions in the *NEW* Standard Chat Thread. I would like to see if it helps clear some clutter and actuall help questions get answered.
For the record - Detain. It changes the board state and opponents options. Mill doesn't do anything to answer board threats