Best case scenario for Earthquake: Your opponent's deck does not rely on non-pillar sources, and the mark is for off-element things. You can play earthquake as the opponent plays pillars, severely choking off their quanta and preventing them from doing anything.
Best case scenario for Breakdown: Your opponent's deck is permanent based. You play breakdown on the 3rd turn, cutting quanta production in half. Later, time quanta accumulates quickly, and you can blast through your opponent's other permanents without much trouble.
Middle case scenario for Earthquake: Your opponent uses their mark for some things, but otherwise is pillar based. You can earthquake their towers a turn or 2 after they get out, but your opponent gets some things out anyway because of the gaps in denial.
Middle case scenario for Breakdown: Your opponent supplements their deck with many helpful permanents. You get out your breakdown on turn 6. By then, the opponent has gotten things out, and you have to deal with permanents that are, in effect, half there.
Anyone dispute these?