Basically what Uguu said. While Quasar may pose a more relevant threat once summoned due to its OTK potential, negation, and floating, it's much harder to get out. Infinity, between the multitude of machine-type archetypes that can make him, along with Ptolemaus, is much more relevant in general because of its accessibility. So, to clarify: if we are to include the requirements to summon and ease at which those requirements are met, Infinity is leagues better. If we assume the card is already on the field, Quasar wins.