It's interesting to see how Pratchett thought about this over two decades ago, given that I have read most of his Discworld books. There is a sharp contrast between witches and wizards in his work. While in many ways his witches do the "dirty work" and the wizards sit in the university, the way it's presented is such that the witches are about helping people and getting things done, whereas the wizards are a bunch of doddering old windbags in slippers who don't really do anything at all...and when they do, they usually screw something up pretty badly.

Granny Weatherwax (a witch) is easily one of Pratchett's best characters. (She shows up in Equal Rites, and then again in Wyrd Sisters, which is a sort of retelling of Macbeth...and in several books since.)