I was considering .NET Core for a project but they appear to have fallen behind the JVM rather dramatically when it comes to GC performance. The JVM now has low latency collectors for very large heaps. Is there any work being done in .NET Core to catch up?
One thing about Microsoft, their tooling just seems more polished and things tend to just work.
I'd be surprised if a lot of start ups don't start using c# since it's now open source and more platform agnostic.