Ella's best years are the Decca and early Verve. Particularly with minimal accompaniment.
"vocal fireworks make for precious little emotion." Maybe you're referring to the later 60's and forward schmaltzy, overproduced "pop" Ella that many think of when she's mentioned?
Billie's work up thru the 50's is where she peaked.
Billie vs. Ella? You can't go there....you just can't!