>>41413038Earthquake is more reliable, but has only 10pp.
Magnitude has 15% chance to be stronger than Quake and 85% to be weaker, but packs a whooping 30pp.
On normal playthrough earthquake can last you through two, maybe three trainer battles, 10 wild ones. Its superior in damage output, but thats it.
Magnitude keeps you going for way longer while still being powerful.
Quake for pvp matches, magnitude for when you are playing through the game.
Get both if you can.
