Whitaker.. I wouldn't even pick Rosario to beat him in his prime, and he was basically finished after losing to Hiranaka in 92'. Pernell still had Chavez ahead of him a year later.
Truthfully, once Chavez got a hold of him in late '87, Rosario was never truly the same. If Edwin had developed like he should have, I would give him a strong shot at taking Pernell. But in this time frame, Pernell would win. I don't know if he would stop Edwin, but he would at least shut him out over 12.
Whitaker by wide decision, but there would be a mid-rounds moment of sudden duress; a fleeting moment of drama and hope for Rosario before the wide points loss is handed to him.