ShreyasRmsft commented the following on GitHub:
Hi @cactuaroid DataTestMethod is not needed.
Go ahead and use TestMethod with DataRows to data drive your tests.
For any more doubts follow the official docs at https://github.com/microsoft/testfx-docs
https://github.com/microsoft/testfx/issues/614
https://github.com/microsoft/testfx-docs/issues/64
So, according to Microsoft, it is preferred to use TestMethod over DataTestMethod.