Couple reasons you might want to try out V2: * precise file arguments; if you say

./pants test project/test_foo.py

, we will only test that file and nothing else * smarter caching * less verbose output * avoids irrelevant work that V1 does - should be faster * works more ergonomically with custom target types * better support for Python interpreter constraints; if one test uses Py2 and another uses Py3, you can still run them in the same Pants run, unlike with V1