What's confusing is the naming.
There are 3 sizes: Small, medium, big.
There's 2 small iPads: one is better than the other.
There's 2 medium iPads: one is better than the other.
There's 1 big iPad.
Easy.
It's the names that are a mess.
Should be one small, medium and big. Pick your storage. everything else is the same. Oh wait it's not.