It depends entirely upon how your boat and it’s bow-eye sit in relationship to each other with your boat fully loaded onto the trailer. You want the strap to be neither higher nor lower than the bow eye... in other words... as level with that bow eye as possible. I have a V-hull in which the strap comes over the winch... and a pontoon in which it comes under the winch. There is no generically-correct answer so ignore those which categorically tell you “over” or “under”.
Look at YOUR boat on YOUR trailer and keep it as level as possible when loaded and snug.