I can't really help with your question exactly but I do know the megapixels aren't everything. A lot of how good a camera is, is really due to it's lenses.

e.g. there's a reason those Mars rovers only have 1 mega pixel cameras (but very good lenses). Some of that may be related to reliability in a harsh environment though. Something I just found quickly googling: http://www.msnbc.msn.com/id/3958138/