I have played both demos and GOWIII is freaking amazing. I have played the demo like 15 times and I have discovered some awesome combos with the cestus and the Blades of Chaos. So, you people that are saying GOWIII is simplistic should really play the demo more and try to discover some things.
In the other hand Bayonetta is also really cool, and has a more complex fighting system; but in the end judging all the aspects like graphics, gameplay and presentation GOWIII is better than Bayonetta and better than every other action game yet this generation. I have DMC4, Ninja Gaiden Sigma 1&2, and after playing GOWIII demo, those games lack something.
I will Buy Bayonetta, DMC5 and Ninja Gaiden 3 because all those games are really cool and rewarding (especially Bayonetta....I love sexy women XD); but GOWIII will be a Masterpiece.
I know this is a Bayonetta thread, and that all I have said promotes GOWIII lol; but in the end both will be great games; so buy them both just like me XD