Because I was curious, I did a test with 3dmark Icestorm three times, averaging 40,000 score with the microsoft provided drivers. I updated the intel drivers to the latest release and re-ran the tests. Scores remained the same averaging 40,000 again, very little margins of variance.
This is on a SP2 256gb fyi.
I think a better benchmark should be used. I had that one. My pro1 maxed out both tests including the extreme one. I think its more for android or baytrail. when I ran the test with pro 1 I maxed both out. use a FPS counter to measure the differences.