I would follow Carrot past the Gates of Hell and back again, and would report it all to Mr. Vimes. Pratchett writes his characters with great depth and beauty, and in his own way makes me feel their joys and pains no less than Rowling...but it's still the difference between Gilbert & Sullivan and Carmen.
Heh... I once saw a praise quote from Piers Anthony about Terry Pratchett that managed to be condescending and insulting at the same time. When good ol' Piers invents a second plot and a fourth character, tell me.
Meanwhile, Discworld's full of characters as memorable as those which inhabit Rowling's world, but in different ways. Am looking forward to a new Guards novel immensely.