Apple is currently offering the best nvdia's GPU they can offer for the power consumption. There isn't any other Nvidia card that offers more performance for the same or less TDP. That's why I doubt that Apple is even going for 425m since it has 96 cores (330m has 48). Maybe GT 520m. Nvidia's policy is to put more cores to get more power, but that means more consumption if they don't shrink proccess nanometers, and they are not doing it.
In the other hand ATI seems to have a lot more of power in OpengGL even in the cards that performs less in Directx than Nvidia ones and their GPUs are more power efficient. That is so convenient for apple. Less power consumption and more performance in openg GL even putting lower end cards..
If you want to be really surprised activate cinebench r10 opengl in the following list and sort the list by that column. You can see how ati outperforms nvidia in opengl!!
One ATI midline 6550 is faster than two top of the line nvidia gtx 480m in sli!!!!!!!
http://www.notebookcheck.net/Mobile-Graphics-Cards-Benchmark-List.844.0.html?&3dmark01=0&3dmark03=0&3dmark05=0&3dmark06=1&archive=0&benchmark_values=0&cinebench10_ogl=1&condensed=0&crysis=&doom3=&dx=0&fear=&month=&multiplegpus=0&or=0&professional=0&search=&sort=cinebench10_ogl&vantage3dmark=&vantage3dmarkgpu=
I like nvidia a lot more, but, since OSX works with OpenGL and not with directx, Apple should take an ati gpu if they want to offer something faster in their new laptops.