EDITOR'S OPINIONI must say that as huge of a Frank Welker fan as I am that I definitely prefer the adult version of Kermit the Frog. That being said I do think Welker did a good job coming up with a 'baby' voice for the character. Steve Whitmire also did a tremendous job taking over one of the truly iconic voices of our time.
However, in the end, the reason Kermit is so famous and such a recognizeable voice is because of Jim Henson. 1st: Henson, 2nd: Whitmire, 3rd: Welker