ReSharper gets a significant number of bug fixes (based on more than 260 requests) and a bunch of features and improvements 

Rider 2018.1 EAP is open

//todo:Do something  
//bug: do something  

• Support for .NET Core 2.0: you can now edit, run, debug, test, navigate and refactor your shiny new .NET Core applications.
  
• Rider 2017.2 comes with ReSharper 2017.2 as its engine for providing .NET support. This means a number of features announced with ReSharper 2017.2 are now available in Rider. 

ReSharper 2017.2.2 fixes the annoying code completion bug with duplicate parentheses 

ReSharper 2017.2 understands .NET Core 2.0and C# 7.1, gets better at C# 7.0,provides more code inspections and context actions including new IEnumerableinspections, delivers many powerful navigation and search improvements, brings new C# typing assists, levels up support for TypeScript, JavaScript, JSON and Angular. 

Rider is a cross-platform .NET IDE: you can use it on Windows, Mac and Linux. Rider lets you develop ASP.NET, .NET Core, .NET Framework, Xamarin and Unity applications. 

In general, to be honest, R# feels smarter. But another aspect here is that with R#, I rarely have to leave my current context, pretty much everything is available immediately from where I am.