It all depends on what you’re trying to accomplish and where you’re starting.
If you’re in pain and are looking to relieve that pain then Stretch & Recovery therapy alone may be your best bet until your pain subsides. Your body will then be in a better position to support your efforts.
If you want to ensure that you prevent injuries while diving into a new exercise program, then you can start both your yoga or pilates program and your Stretch & Recovery therapy program at roughly the same time while expecting outstanding results.