Ball flying towards me or me flying towards ball
Look at it this way:
Suppose you are in a train travelling at 10 m/s. Somebody inside the train throws a ball at you in the opposite direction at 10 m/s. You feel the pain belonging to your first experiment. However, somebody looking at this experiment from outside the train would say that the ball is standing still and you are travelling towards the ball at 10 m/s (= your second experiment). Since it is the same experiment, you will feel exactly the same pain.
Yes, unfortunately. Because of the equivalence of inertial reference frames, the the physical laws are the same in both reference frames.
However, another possibility, which is non abelian, is that instead of feeling the same amount of pain, you could be feeling the opposite amount of pleasure. It depends if pain (X) are fermions or bosons, that is, if their function is symmetric or anti-symmetric.
Let's take everything out of our scenario other than you and the ball. No baseball stadium, no Earth, no spherical cows, NOTHING in the entire universe but you and the ball. (Nope, not even microwave background radiation)
Now the question has changed. Now you need to ask whether it's possible to decide whether you're moving towards the ball or vice versa.