Wilander had problems with motivation in the smaller tournaments. Wilander's game required him to be utterly focused if he was to play well, because he didn't have a cruise game like Becker. And Mecir was his toughest opponent of all. If Wilander didn't start well against Mecir and hold his serves early on, he would be crushed.
As for the Wilander vs. Becker vs. Edberg arguments, you can make a case for any of them being better than the other two. My personal belief is Wilander>Becker>Edberg.