My favorite Mac LP is Live in Chicago, but of the two women in question, my nod would go to Christine. Partly because I think she is the superior song writer, and therefore sounds better when singing her own tunes.
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.