apples and oranges

apples and oranges {esp. US} (used to describe a situation in which two people or things are completely different from each other) — несопоставимые вещи, явления, понятия; то, что никак нельзя сравнивать
~ *мухи от котлет (?) (в ограниченном контексте)

They are both great but you can't compare apples and oranges.