Both the Adams and Harvin trades were the worst in franchise history IMO, but each for different reasons. Yes, Harvin did contribute in the SB, but he did absolutely nothing to help get us there. And, he nearly destroyed the team, by getting into a fight with Golden Tate, refusing to go into a game forcing a trade...the locker room was so split that Beast nearly didn't board the bus to the airport after learning of the trade. And there were red flags galore that were ignored or rationalized, the worst of which he once chased his head coach down the sidelines during a game, screaming his lungs out at him, complaining about a QB decision. Pete's ego was such that he thought that he could tame a shrew, that through the power of his personality, he could succeed where others had failed.
The Adams trade obviously had some unforeseeable events in all the injuries, but he was traded for without a clear vision as to how to use him. He initially thrived, but that was in a vacuum where our pass rush was on pace to be the worst in league history. Once defenses figured him out, he was no longer effective in that role, and he was a one trick pony, sucked in coverage, not a ball hawk who had interceptions bounce off his face mask.
So it's a tossup. Yes, Harvin did contribute something in our SB victory, and he was a little cheaper as we only traded a 1st, a 3rd, and a 7th vs. Adams' two firsts, a third, and a player. But although Adams' was more expensive and didn't produce outside his first season, we can't ignore the role injuries played in his demise.