Let's say you're Gaston, and while your deck is a fairly typical midrange Limited deck with an average curve, you know that Belle's deck is extremely aggressive, full of two- and three-drops
Brutally difficult to pull and even rarer in PSA 10
The option of checking to see if your top card is worth drawing before cracking your Scalding Tarn far outweighs the potential benefit of seeing a card from your opponents hand
The Lens of Format-Warping Impact Some cards are so influential they fundamentally dictate the rules of engagement
Cons: Less personal, might need upgrades (and more cash) to be optimal, power levels can vary between decks, and not every card will be a winner
If you get Mewtwo EX onto the field quickly, start with Psychic Sphere to apply pressure with its low Energy cost while you continue setting up Gardevoir