F# also has substantially better type inference so you don't need to write the types out everywhere, type aliases are first class too so you can easily write out some helper types for readability.

You can pipe a monadic type through various functions writing little to no type declarations, doing it nicely is F#'s bread and butter.

In C# version n+1 when the language is supposedly getting discriminated unions for real this time I still don't see them being used for monadic patterns like F# because they're going to remain a menace to compose.