Deep code profiling of the JVM is still a lot better than Linux .NET Core. I still like C# though.
Probably, haven't tried really on .Net but Java is awesome.
Another point where it is really hard to get people to actually understand the magnitude of the difference is in IDE support, what exists and what you get out of the box.
I mostly enjoy programming in .Net Core a lot but there are times when the difference becomes extremely visible.
As someone with background from Java but who has worked a lot with .Net Core lately, I guess it might depend on what part of .Net you talk about.
.Net Core worked extremely well on Linux for all use cases I saw, mostly web applications, cli tooling and batch/queue processing. I cannot remember a single case where we had actual problems because of Linux.
In fact, FWIW for small console applications it ran extremely much faster on Linux than on Windows, on the same hardware.