I work with NUnit only. It is pretty good for me. It is integrated into different add-ons for Visual Studio like Resharper, it supports in TeamCity and it has stand-alone test launcher
And looks like NUnit become an industry standard for unit testing.
And we haven’t had any major issues with Moq or Rhino.Mock.
As I remember Asp.Net MVC (I worked with 1.0 only) uses MS Unit. You may easily switch from MSUnit to NUnit.
A similar question was asked already, maybe you find some details here:
NUnit vs. MbUnit vs. MSTest vs. xUnit.net