THis is actually a very good idea for a fantasy matchup, and I'm not sure that I've seen it here yet before. Anyway, I think it safe to say that both of these men probably peaked right around the same time, say 1980-1982. It would be a good match between a very durable and decent boxer in Berbick vs a large hard hitting puncher and a fast starter in Cooney. Trevor had good wins over Tate and Page during the early 80's while Cooney at least looked impressive at dispatching past prime stars in Norton, Young and Lyle. Cooney would have the size and power and Berbick arguably the better stamina, chin and maybe a slight edge in boxing ability. Cooney would start off fast and probably land some big shots that would keep Berbick on the defensive for a few rounds. After things settle down and Gerry starts to slow up a bit, I can see Berbick going to work, landing some decent shots and doing some catch-up work on the cards. Both men would probably fight until they were pretty well exhausted and fairly beat up. The only way I see Cooney winning this fight however, is of he's able to stop Berbick early ( a very real scenario, but not likely. ) Trevor was only stopped by two big punchers in his career, one of whom he fought in his 11th pro fight, while the other he met later in his career and who's sir name was Tyson... But in 1982 at the age of 27, with 25 pro fights and wins over Tate and Page, He was fairly durable. Of course Berbick was no Holmes and couldn't land on Cooney as often or as accuratley as Larry could. He also didn't have quite as much experience at going 15 as Holmes. Therefore, I can probably see Berbick winning a very close decision in what would probably be a very crowd pleasing fight...
Berbick was a very durable fighter, but Cooney had nuclear power in his left hook. If it landed, Berbick would be gone. Gerry would be a little bit too big for Trevor and I'd favor Cooney by fifth round stoppage.
If Berbick could take Cooney into the late rounds, he might have a good shot with him. But he didn't have good defense, and we've seen how he was vulnerable to punchers early.
Gerry would catch Trevor with that left hook, and end it within the first three rounds.Berbick is in no condition to deal with Gerry.