One has structures, ARC, proper extensions, good protocols/interfaces, flexible enums, and runs natively. The other one doesn't. I think I'll choose the former.
One has a top-notch IDE from a top-notch IDE vendor. The other has XCode. Also, ARC aside, for the 3-4 items you mentioned, either Kotlin also also has them, or has just as good alternatives. And none of those are life-changing. ARC vs a good GC is just a different tradeoff (no cycle detection vs pauses, etc). I'm sure you can find some things where Swift is better at, and others where Kotlin is. But not that many to…
When will Jetbrain have a decent interface builder?
Decent instrumentation?
Decent documentation viewer?
Can you get an object graph with JetBrains?
Xcode isn't perfect, but it's way better than JetBrains.
Just because one has one feature that one doesn't have, doesn't mean that Xcode beats JetBrain's IDE all day.