Being "stuck" with a 5mp shooter is neither here nor there. To be honest, in the past I've had 8 megapixel cameras in my phone and I still turned it down to 5 in the options because I have no need for 8 megapixel pictures.....most people have no use for taking huge pictures, and that's all you gain from more megapixels. It doesn't mean a better picture. As for comparing the 2 cameras, thus far the side by said pics I've seen the Galaxy Nexus either looks better or it is about even. One thing that the galaxy nexus wins hands down though is the shutter speed. It isn't even close. Take a look at this link and you'll see what I mean (they take about 6 shots AND THEN STOP...in the same time it took just to get 3 shots on the 4s).
http://www.youtube.com/watch?v=n0fN55W9erM