I think Pryor by decision. He would use his funky movement to make Frankie stalk him. Aaron would have to be very wary of Randall's excellent straight right, though. It was similar to Arguello's. Pryor survived Argeullo's best right hands and I assume he could survive Randall's as well.
Randall is an interesting fighter. 58-18-1, but 13 of his losses came after turning 38 years old. At 34-36 yrs age, he was fighting round robin championship title bouts win Julius Caesar Chavez and Juan Martin Coggi, both top fighters, before beginning to fade with a title defense loss against a younger Khalid Rahilou.