I could argue that this is her best, but any way you look at it the performance itself is unarguably stellar, liquid gold.
Postscript: Calling Aretha the Queen of Soul can be a bit fraught: some of her performances are good, but they are not all outstanding. But if you listen to the right ones, carefully enough, it is clear she is Queen. Another recommendation is 1973's Angel. Not as big as the follow-up (Until You Come Back To Me), I still heard it plenty at the time, but paid little attention. But Angel is, however, yet another example of how Aretha can outshine them all.