serendip

The white balance is the most obvious difference.  Google's falls short significantly in some cases.

In general though image quality is rapidly approaching "good enough" status from the major module/lens manufacturers (Chicony, Foxconn, Largen, etc).  Most of these pair comparisons can be chaulked up to photographer preference.  The expertise of these module companys are reaching a point where you can almost drop in any module and get to a point where most people aren't going to notice major differences most of the time.  The fixtures in the factory are pretty much locked in place for calibrating these modules and the sensors all come from same companies.  The differences are now mostly in post processing (bokeh, studio, etc) and are "cute/cool" features that's don't really impact general usage.  Gone are the days where a crappy phone will produce obviously eye sore images 80% of the time (though there are exceptions).

I spend most of my time now on designing and calibrating camera modules for data collection/AR.  3A (AWB, AE, AF) is taking a back seat to intrinsic, extrinsic camera calibration.  You'd be surprised how much a module varies from an individual phone to another.  Same phone, same module, same conditions and the optical center or view angle can be way off but still undetectable.  Minor differences that can't be seen by a person taking images/videos translate into inches when trying to grab data out of camera pairs.

That's where Apple has a serious advantage right now.  They make all the hardware.  The know exactly what the tolerances are and how well the cameras' are calibrated for each product.  On the Android side, you have Google trying to make post processing software while dozens of companies are making the phones with whatever camera specs they want.  It's like trying to herd cats vs cows.

IMHO..
I've worked on cameras at Apple, Nvidia (Tegra 2, Android, HTC, etc), and was head of image quality at a fairly successful camera startup so I'd say I'm fairly unbiased.