[AsyncAwait]

A lot more emphasis on functional programming & nicer syntax around it, preference of value types over reference types and immutability by default/opt in mutability, nicer parsing with Codable, nice pattern matching and destructuring syntax, native binaries by default, more flexible memory management.

[The_rationalist]

Modern C# has both destructuring and pattern matching in switchs. The memory model of swift seems obscolete, reference counting does not catch reference cycles and swift isn't faster than C#

C# isn't really missing features vs swift but it might have a less modern syntax

[AsyncAwait]

In regards to the memory model, I am not talking about reference counting, but rather [1].

1 - https://swift.org/blog/swift-5-exclusivity