It's really just a question of if you would rather have the card be luck based, or strategy based. Of course pretty much every way the card could work would have both of these elements, but certain ones could be emphasized. If it's a random card you lost, it's luck, if it's a card you choose, it's strategy. I would personally prefer the emphasis on luck, because it's an element I feel this game lacks a great deal of. The only real luck is card order, quantum generation, and mutants. Unless I'm forgetting something.