Witch vs Knightess: Which do you prefer?
My answer is very subjective, I prefer witches because I am an immortal magical girl.
When in doubt, both.
And over the course of my stories, both are frequently seen.
Some stand-out examples of both in said stories are:
Ravenna in The Elarian Chronicles; Duskfall, and the sisters, Aliya and Mikala in Aestelle Nocte.
Though none of them have been introduced yet in the respective stories, they do have relevant supportive roles within their respective casts.
Ravenna is the Fiendling Witch that joins up with Morrigan over the course of volume 1, and is often the voice of reason within her adventuring party.
Aliya and Mikala are the surviving members of Princess Seiara's entourage that land on Earth with her, and serve primarily as the Princess' guardians and handmaidens, and are rarely far from the Princess' side.
I can't say much more about them (without spoilers) though.