There are many more variables than just looking at numbers. It matters what operating system your in (Mac OSX seems to have better performing drivers for the Intel HD3000) and the game. A game like Call of Duty 4 is completely GPU bound, so the stronger GPU of the 320M shines through. A game like Starcraft 2 is almost entirely CPU bound, so the better CPU of sandy bridge shines through.
How come the 2010 MBP wins in Starcraft 2 then? Starcraft 2 is FAR from being entirely CPU bound. Maybe if you run it at lowest resolution with everything at minimum. But if you run it at better settings
you will be limited by the GPU.
I can agree with you regarding the HD3000 having better drivers in OS X. So there the difference is smaller. But if you look at the Windows tests the 320m MBP gets up to 35% higher FPS than the HD3000 one.
It all boils down to what you do the most, if you encode loads of video then you'd want a better CPU, if you play games you'd want a better GPU.
Windows drivers suck for HD3000.
OS X drivers are far superior for gaming.
Too bad you need Windows if you want to play most games .