I'd rather have the dynamic range, aperture, and so forth, than more megapixels. That's not to say I'd gratuitously turn down more, but, say, 10 as opposed to 15 megapixels doesn't bother me.
Thats where I like double blind tests - e.g. I printed pictures from the same shooting but taken with different cameras in large format. Ask unsuspecting (but not inexperienced) Audience to judge image quality. Conclusion: 12 or 21 MP, it doesn't matter.
For dynamic range, try processing video shot with a 5D2 right after your worked with footage from say an arri alexa. I want the same DR for photography.