BoxRec

15 Rd Jr Welterweight
I searched but couldn't see this matchup.

At 154, Benitez scored an easy win over Duran. But Duran didn't seem motivated.

What if they fought at 140,? Duran would have been much quicker and harder punching than at Jr Middleweight.
Benitez was slick, but could he have evaded Duran for 15 rds? I think Duran would counter the counters of Benitez and stop him by the 10th Rd.

Duran wins at the weight you proposed. He'd stop Benitez late if it's a 15 round bout.

Duran was suffering the career crisis, when he lost to Benitez. Probably on a different occasion Duran would have won even at the weight where they actually fought.

Roberto Duran at 140 or 147lbs, beats Wilfred Benitez. Especially, the Montreal Duran beats any version of Benitez.

I'd favor Roberto, for Sure, at 140.
8-4 in a 12'er.
10-5 in a 15 Rounder.
Probably not an epic bout though. I can envision Benitez getting extremely defensive minded by around the 8th round,in this particular hypothetical. It's still a Very Good bout, Especially for the first 5 rounds though.