Seems like there's plenty love for vocalists on this board.
Most controversial are the white males: Chet Baker, Woody Herman, even Sinatra.
I have to admit that I have trouble with the first (love his trumpet, however), can tolerate the second, and am a big fan of the third.
Vocals can be an acquired taste, but one well worth acquiring. I am a fan of vocals, but take each singer on a case by case basis. Often, the most dated aspect of an old record is the vocal, and it can take a while to hear through period mannerisms to separate the great singers from the average to poor ones.
With scat singing, a little goes a long way. Besides Ella and Louis, just about nobody can pull it off, certainly not at length. And vocalese can get annoying fast.
Once you get past Bessie and Billie, is there any singer that everyone agrees on?
(Maybe Aretha?)