If I'm just holding the same target power, I don't think it really matters to me. I spend a lot of time climbing, and a headwind more closely mimics the demands of a climb, so I don't find the greater deceleration forces to be much of a problem. Coupled to that, I'm lucky to be able to hold a fairly aerodynamic position with a flattish back, so I don't pay as big of a penalty for headwinds.