Hearthpwn

Unlike Shadow Visions it doesn't produce another copy out of thin air, so it prevents certain nonsense combos, which is good.

Shadow Visions but slightly worse... Eh, better than nothing I guess.

True that. Should see some play in wild cycle OTK decks with Gadgetzan Auctioneer and 2x Radiant Elemental

Shadow Visions but slightly BETTER. It's a powerful card draw 

Drawing the card is, at best, situationally better than discovering a copy. But most of the time, you're gonna want more uses of the spell you're discovering.