Both excellent. I would say that John Buscema was more of a natural artist, but John Byrne was better and more sensitive about capturing subtle emotions–his character acting was better.Some of this simply boils down to what each artist was most interested in. Buscema could do anything, but he tended to remain at a remove to the stories he drew, and so his characters tended to “act” more broadly, like theater performers playing for the back of the theater.