Ohhh interesting! I think you answer your own question - the one fit where Sam wins is when he is possed by the Meg!demon. So again here in 4.21 it is really not!Sam who defeats Dean. (there is also one other fight - the one in WIAWSNB which is a replay of the one in the Pilot).

And I am thrilled to find another way in which Sam=Peter!! Thanks for that!