Quote from steve_man »you need to be playing a deck that (a) cares about having a Lotus Petal, (b) cares about casting Careful Study
What deck UR(x) deck (or any deck really) wouldn't care about mana ramp / fixing and card filtering? I'm confused to see people say things like "needs a deck that cares about the graveyard for Careful Study". They're looking too much into the graveyard aspect but completely overlooking the fact that it's also just card filtering.
It's not that having a Treasure or having access to card filtering is ever bad. It's that if you use Prismari Command to burn a small creature and make a Treasure, you're not getting a 2-for-1 the same way you'd be getting a 2-for-1 if you used KCommand to burn a small creature and make your opponent discard a card. You're getting a 1.5-for-1. I'm saying that Prismari Command was more cautiously designed than KCommand, and that it won't be as much of a no-brainer across all formats, not that it's worse in cube; cube is the one format where the two cards are similarly powerful and flexible because it's exactly in powered cube that you see a lot of mana rocks, use a lot of graveyard tricks, and run opponent-can't-draw effects.
Edit: I was being unclear/misleading when I wrote "narrow circumstances." I meant something more like "specific circumstances, which are more likely to arise in powered cube than in nearly any other format."