Martinez or Spinks. Come-forward guys like Williams and Margarito still may cause him problems even if he's taken a more boxer-type approach.
I'd love to see Cotto just get maybe 2 relatively simple wins under his belt, perhaps a Foreman rematch and Spinks or Dzindziruk. Then go chasing Williams, Martinez, or even Margarito. However, i don't honestly think Miguel's heart is in it enough to fight on for 2 or 3 more years, so i think his next fight will be another tough one. In that case i voted Margarito. A lot of people would say, "he shouldn't face him, Margo will always cause him problems plus he's mentally damaged from their first fight". But they easily forget the damage and problems Cotto di to Margo! Also Margarito himself will have doubts after the whole handwrapping fiasco that has been analysed and analysed again and again. I think if that fight was tomorrow, based on what ive seen of both Cotto and Margarito's comebacks, Cotto wins a points decison of knocks him out late on.
Gimme Cotto/Berto or Cotto/Williams. Both very beatable opponents for Cotto, and both are fights with risk and reward.