I'll vote for Benvenuti. Great amateur pedrigree and experience...Both would cause each other stylistic headaches. So it would boil down to who makes the adjustments, and stays consistent with out mental lapses (ie 12th round meltdowns). I think Benvenuti's resume says he would be the man. Benvenuti was a very good boxer, who often gets overlooked...I like Nino by decision, because he could fight more effectively either pressing or countering than Martinez can...in other words, Benvenuti is the more well rounded fighter.
I think Martinez' style would give Benvenuti more problems than Monzon's style and technique did in both of there fights. Martinez, besides Hagler and Hopkins, is another guy that I'd pick over Monzon although not by much at the moment given that he's still a natural Jr. Middleweight fighting as a world middleweight champion. Martinez by a fairly close but unanimous 15-round decision.
I like Martinez' jab and athletic ability to carry the day. 15 rounds? I like Serg by about 9-6 nice and clear.
My pick would be a peak Benvenuti every timeMartinez is an excellent boxer but IMO slightly overrated when talking ATGs.But over the distance.