Can both be right?
Ordonez' home run pushed Detroit into the World Series. It erased a long history of futility. But it was the bottom of the 9th of a tie game in a 3-0 series. The series wasn't definitively over yet with him at bat, not until he pushed a run across the plate. But it seemed inevitable that Detroit was going to win that series.
That Prince block in the playoffs saved the series for the Pistons, didn't it? That was a pivotal moment. I don't like pointing to one play in a basketball game and saying that was it, save for end of game stuff (ie, don't leave Horry open).
I think there's merit for both from different angles. I think I'd say Prince's block was bigger in the moment.