I believe graue was referring to the case when you are not using such a type in the code; then you have a guarantee that the value is non-null. The purpose of the Some/Option/Maybe types then becomes to indicate when a value can be null, but outside that wrapper type it is guaranteed to be non-null. So code where it must always be non-null does not have to confirm that that's the case. I think it is less about efficiency and more about not having to worry about it.