What is the benefit of removing redundant imports in VB.net or using in C# file

Beside the fact that it cleans up your code, you can also minimize 'name clashes'.
For instance, when you have 2 types with the same name in different namespaces, and you do not use any type from one namespace ... You then do not have to specify the namespace of the type when using it, it keeps your code cleaner.

It removes redundancy, which is a good thing. And its easy to get most of the needed using directives back, by pressing ALT+ENTER (with R#) or invoking the smart-tag by pressing CTRL+. (without R#) on the class that needs it.

On the negative side, you might lose sight of available extension methods, especially when the System.Linq namespace import is removed.

It'll reduce the size of your source code (very slightly), but also improves code quality in my opinion. If you only include what you need, it makes the intent of the file that much clearer.

If you're including a library you don't need, and I'm reading your code, I might end up wasting time trying to figure out where you reference it or why it's used.