Why the either/or? Why must we humans insist on rating and ranking incommensurables? Christine is a great writer/vocalist. Stevie is a great writer/vocalist. Neither is the GOAT, but then who is, or should be? Is anything better than Della Reese's Puccini adaptation "Don't You Know?" Depends on the mood and the occasion. To the best of my knowledge, Christine Perfect McVie has never written or performed lead vocal on any song that wasn't a straightforward love song. But that's her genre, and hers are always sincere, never sappy. Stevie Nicks covers a wider range in a more abstract way, but is more distant, less warmly lovable. Take your pick, depending on mood and occasion. But "who's best?" is a false forced choice which I decline to make. Except that Christine doing "I'd Rather Go Blind" with Chicken Shack was a hell of a launching pad.
Nicks or McVie.....
Which singer do the fine people of Audiogon prefer? In the past, personally, I always preferred the sound of Stevie Nicks. It was in the early 2000’s that the show South Park lured my mind into thinking Stevie Nicks sounded like a billy goat. Having mostly cleared my mind of such nonsense, McVie is still my preferred set of female vocals. Fleetwood Mac is a fine institution regardless of who happens to be on lead vocals.