Pre-Tito Vargas was plain and simple a better fighter than Martinez. I think he breaks him down and stops him circa 10-11.
Vargas was far more adept at dealing with movement and angles than Pavlik. Pav was murderous if you stood in front of him, but clueless once given angles. And Williams, though very fun to watch, simply wasn't that good.
Based on styles, Pavlik would be too big and strong for Vargas. Vargas beats the Hell outta Williams. Paul Williams is quite possibly the most overrated fighter of the last 20 years. People are afraid to say that due to his situation, but the man was not that good.