If you one among the people who think mega pixels doesn’t really matter in the clarity of a photo, here’s something to substantiate your theory. We have a couple of sample photos from the Xperia S (12MP camera) and the Xperia arc S (8MP). From what we see through our eyes it’s evident that arc S’s 8MP beats the S’s 12MP.
Arc S delivers a better snap in low light and normal light conditions. Just see it yourself.
Xperia arc S Samples Xperia S Samples