Both in their prime.

Duran fought and defeated much better competition at 135 than did Mosley.

Duran's ability to slip punches at close quarters while still being able to remain offensive would be the difference.

His defense and craftyness gets him through a war over Mosley's speed, power and crisp combos.

but

Mosley looked unstoppable at 135.

I think Mosley outboxes him. Leonard style.

He's at best in the exchanges at mid range or even up close.

The Lightweight version of Mosley was something different, his blend of power and handspeed was deadly