GOW will please the fanbase, but for somebody like me that has played a bit of GOW and a bit of DMC and is not really biased in favor of one over the other, Bayonetta just appeals drastically more.
Having played the demos, GOW 3 plays almost exactly like 2 but prettier. Not that that is a bad thing, they were great games. Like I said, it definitely will please the fanbase. But just like GOW was an evolution of games like DMC, Bayonetta is the next evolution and GOW is just window dressing an old favorite. Doesn't hurt that Bayonetta has insane amounts of style and charisma as a game either. I mean the music, the art design, the animation, the over the top attacks, they are all insane and top notch.
GOW3 will be a fan favorite, but bayonetta will be used as the future blue print of action beat 'em ups. Just like DMC was the blue print, and GOW innovated on it in the last generation, bayonetta is building on the shoulders of all the previous greats. I am getting it day 1.