This is a tough one. Bobick was more skilled. The Leon that beat Ali though, had tremendous heart and tenacity. But if you look at a common opponent, Scott LeDoux, Bobick kicked his ass twice, whereas Leon was held to a controversial draw. Bobick is a safer bet. But the hell with it: I'm taking Leon, because I like him better and he was way more fun.
Bobick Never had the durability to be a fighter....at least a pro fighter. Spinks although his career fell apart early because he was brought along way too quick was an excellent and well conditioned brawler. Spinks at his best Kos Bobick within eight rounds. Competitive until Duane is hit and hurt...then it's over.
If Spinks was on, it might resemble his bout with Bernard Mercado. If Spinks wasn't, Bobick could stop him. Pick-em fight. Would've been interesting to see.
Bobick was a better fighter than most give him credit for. He had decent skill and power. He just lacked durability. But you generally had to have a good punch to take advantage of his fragility. Leon might have pulled it off, but as mentioned he'd have to be in top form. I can see this going either way.
Leon by split decision. He made it to the top, Bobick didn't. Doesn't mean that Duane would lay down and take the loss. It would be a good fight, but Leon has enough on his best to edge him.
Bobick took waaay too many punches from even class D opponents, and would have been, despite technically a better fighter than Leon, overwhelmed by the sheer physicality of Spinks. Too many unanswered punches absorbed from Neon Leon by the 6th round and the ref would have stepped in to save a badly beaten Duane Bobick.
I personally do not think Spinks had the power to put Bobick away, but, Duane had the boxing skills to win a decision. Spinks was a light heavy in the Olympics.
Spinks absolutely had the power to ko Bobick. Most fighters had the power to ko Bobick. Bobick was brought along fighting tomato cans and fell apart as soon as he was hit solidly. Spinks at his best destroys him.
Duane couldn't punch like Gerrie Coetzee...not even close...he had nothing to use to keep Spinks off of him...to earn his respect, and he had such a porous defense,...witness the Fred Houpe fight when he got hit over and over and over again...nevermind the Norton/Tata/Knoetze bouts. Leon would tag him and keep on tagging him until he fell, or got rescued by the referee.