What exactly is better in Rider?
Anecdata time. I was working on codegen in C#. So I wrote the codegen in netstandard2.1. That is until a team member that used Visual Studio complained it didn't work for him. So I had to rewrite the thing in netstandard2.0 (shudder) and it worked.
I haven't seen anyone that wanted to go back to VS after using Rider. I did use it for a while, but after Rider it just seemed like an inferior version.
How is autocomplete better in Rider? Faster coming up with suggestions? More helpful suggestions? IntelliSense and IntelliCode in latest VS versions is pretty decent...
Performance in VS has improved since going 64-bit.
What refactorings are unique to Rider?
UI? What features?
Your statements smells of preference and sound vague.
I know Rider/ReSharper can fix variable names that are mentioned in comments, which VS can't do (and it gets on my nerves when I don't have ReSharper).
Also, it's been a long time now since ReSharper was "needed" to work in VS. ReSharper also bogged down VS a lot.
https://i.imgur.com/mD6Z4zO.png
Idk if it comes with VS out of the box or comes from
free extension called 'Roslynator', but eitherway it is there.
Because it is. My preference, never claimed it wasn't one. But I don't know people that would recommend anything else. VS Code is faster but poorer refactors/debug experience. It was just a subjective concensus.
I haven't timed the IDEs nor do I intend to in near future.
I think overall the helpfulness was better, and support for bleeding edge features like CodeGen, but I haven't used VS in like year or two.