When comparing xUnit.NET vs MSTest, the Slant community recommends xUnit.NET for most people. In the question“What are the best unit testing frameworks for .NET?” xUnit.NET is ranked 1st while MSTest is ranked 4th. The most important reason people chose xUnit.NET is:
.NET Core area etc.
Ranked in these QuestionsQuestion Ranking
Pros
Pro Supported and used by Microsoft itself
.NET Core area etc.
Pro Extensible
xUnit.NET has an impressive list of extensions which other testing frameworks are lacking.
Pro More intuitive than other testing frameworks
xUnit.NET uses intuitive terminology and is frequently updated to be more lean and user-friendly.
Pro Visual Studios integration
MSTest is fully integrated with Visual Studios and works natively without the need for any plugins.
Cons
Con Lack of documentation
Compared to MSTest and NUnit, xUnit.NET lacks documentation.
Con .NET 4.5+ only
Isn't available prior to .NET 4.5.
(As of today 2018, this isn't really a disadvantage)
Con Bad at bridging technologies
MSTest is better suited for only using Microsoft technologies rather than mixed technology environments.