I still don't get this whole "head voice" argument. Patti uses hers when needed, which is to be seductive or vulnerable (The Actress Hasn't Leanred the Lines, Eva's Final Broadcast, Don't Cry for Me Argentina, I'd Be Surprisingly Good For You), but when she needs to be powerful, which is basically 85% of the show, her voice reflects that.
I find that the fact that Madonna uses her head voice more often on the soundtrack isn't an artistic choice, but simply because she can't reach the notes any other way.
As a side note, I really don't care for Elaine Paige as Evita. She is a case study of using her head voice in all the wrong places, the most extreme examples being "Buenos Aires" and "Rainbow High." She's got a beautiful natural sound and she sounds lovely on "Don't Cry for Me Argentina," but her voice just doesn't have the strength that is required for some of the songs. For strong vocals other than Lupone's, check out Loni Ackerman on "that site." She adds an extra G to "A New Argentina."
"Sing the words, Patti!!!!" Stephen Sondheim to Patti LuPone.