Benitez won against a better opponent and was only 17 year old (although I read recently his age was a lie but never followed up on it) or Mike Tyson becoming the baddest man on the planet by becoming Heavyweight King at just 20. What's a more impressive accomplishment?
Benitez takes this by quite a margin, Tyson looked great vs Berbick, but it wasn`t much of a test, Trevor just stood in front of Tyson and gave up on punching because he couldn`t land anything, he was awful.
You won't find a bigger Tyson fan than me, but outboxing one of the greatest junior welters of all time at age 17 is more impressive than blowing out Berbick. Benitez wasn't even a finished product against Cervantes either. I'd argue that he matured and turned in a more controlled masterclass against Palomino. Then of course, the Duran fight was his apex performance, and one of the finest boxing clinics in the sport's history.
IMO definitely Benitez! Unfortunately he, off and on, let that talent slip away with his 'issues' as the years passed.