Tony I think you fail to understand what "pound 4 pound" means.
Pacquiao, or Maywather, are pound 4 pound #1, depending on who you like more, but no one would expect them to beat Chad Dawson.
Similarly, one could make the argument that Pacquiao is pound 4 pound #1 but would lose to mayweather based on size (if you fall into the camp that believes floyd is too big for pacquiao).
See what I'm saying?
I don't know how much of a factor size would be in a showdown between pac vs floyd, but what I do know is that floyd has been a WW for 5 years and pacquiao has been a WW for less than 1 year, and was a lightweight less than 2 years ago. So you know, it really could be a factor many people are overlooking, especially considering how bulked up floyd has looked in his previous two fights (I stated my observation was that Floyd looked to me that he was close to, or over, 160 pounds against shane on fight night).