Good while it lasts, but Briscoe is stronger than Nino. Bad Bennie batters the little Italian for a late TKO.
Benvenuti wasn't a "little" Italian...he was 5'-11", a legit middleweight and pretty rangy, as well as being a better puncher than he's usually givben credit for...but I do think that Bennie was too strong for him, and would have either, as you say...worn Nino down for a late tko, or would have decked him a couple of times en route to a unanimous 15 round decision..probably the former result.
Briscoe could take the fight to an unprepared Benvenuti and win but Benvenuti in his best form could potentially win a decision. Briscoe was strong and durable, but very one-dimensional in his approach and beatable. Nino however doesn't really have the punch or the physical strength to keep Briscoe off of him for a comfortable win.
Briscoe was one of my favorite fighters but unless he caught Nino unprepared I think Nino was the better all-around fighter. Nino has quite a resume...Nino by close UD, surviving some rocky moments