In 92-94 Courier was at his peak. Arguably Edberg's peak might have been more like 88-91.
But Courier was one of a group of players that ushered in a whole new level of pace in the men's game. From what I saw when Courier started beating Edberg Courier could deal with Edberg's spin, and dish out enough pace that those beautiful volleys of Edberg's weren't quite enough often enough to get the job done. Edberg could not dish out enough pace to keep Courier off balance enough of the time to prevent Courier from setting up and firing.