This is most effective if youve got some strong enter triggers out on the battlefield, but either way Id save this in your hand until you need it to dodge removal or a board wipe
If there are a few Dragon enablers you like for your decks on the cheaper side of life, pick them up now
Have you ever looked at Dragon Throne of Tarkir longingly, but ultimately passed because of how much mana it costs to get that very first activation
If Paralyze, Sleep, Poison, or, heaven forbid, Confusion ever become super popular and powerful, Chaos Tower will be there to keep them in check
The moment you run out of cards that you can play usually spells that youve already lost the game because you can no longer keep the tempo you were building up and have no resources to maintain your board state
The first scenario seems like it will produce more damage but the second is going to net me more life