On the stage Zan Charisse is definitely number 1. She is the best dancer to tackle the role of Louise and her acting was fully believable.
A close second among the three I have seen is Tammy Blanchard, who was spectacular vocally, probably the best actress and singer ever in this role on stage, but despite her excellence in retrospect I tend to agree that Louise was not a good fit for her talents.
I have not seen Sandra Church or Crista Moore but one I did see and my least favorite, despite all the raves and the Tony, is Laura Benanti, who after the transformation to Gypsy Rose Lee, was not believable for a second and I don't particularly like her singing. The real Gypsy Rose Lee was beautiful but also clever, witty and never crude as Benati came across to me in the role. I realize this is a minority opinion but it is my own based on the performance I attended.
The greatest actress to have played Louise is by a gigantic margin, the late Natalie Wood, in the 1962 film version. Not one of the three actresses I saw in this role on stage can even come close to the charm, vulnerability and sheer sexiness she displayed as Louise. Simply put, Natalie Wood WAS Gypsy.
My Avatar is the amazing young singer, James Anest