Between Callebaut bulk and Ghiradelli bars, I prefer the Callebaut, but it is all a matter of personal taste, either, or both, will work. You could do your own taste test!
My white chocolate hierarchy is as follows:
3 Callebaut bulk
4 Ghiradelli bars
I don’t think I’ve ever tasted Valrhona Ivoire, it’s sort of funny because the dark bars are available here, but not the white.