OP posited 1995 for Whitaker and 1985 for Curry. Pernell was 31 in 1995 and Curry was 25 in 1985. I'd say 1993 Pernell may be slightly better than the 1995 version but not substantially.
I think that Donald Curry would have been in a dust devil of a match against Pernell Sweet Pea Whittaker. Sweet Pea's right jab, and his movement would have made it a long night for Donald. But Curry did have a good right hand that would be the weapon to use against southpaw Whittaker. Curry would cut off the ring at mid fight. I see Donald rallying to take this fight on points, as he was crafty as well. Plus, Curry was the natural welterweight.
Whitaker's defense is rarely matched but Starling had great defense himself too. At one point he was one of three boxers Futch named as having the best defense in the game.
Whitaker is the better fighter. But then again curry was pretty awesome at welter. Would be a close one