I'm finding that my polarizer is also working better on the full frame sensor.
I'm not sure exactly how or why but I am noticing that the filter is covering more of the sky and making it noticeably more even as well.
Here the polarizer has only made a very slight shift in the blue of the sky to the very top left of the frame. This is a much better performance than when I was using it on the 400D crop sensor. I think that it is possibly that I am just able to see more of the polarization affect in the view finder and therefore I am able to balance it more precisely.