Comparing Intel HD 620 vs Intel Iris Plus Graphics 640

I'm weighing the possibility of picking up a Surface Laptop and there is an option between these two graphics chipsets and I'm having a lot of troubling finding good information about the Iris 640 and a comparison between the two.

Are there any good comparisons of performance between the two? I'm not expecting console gaming here just trying to get an idea of how much better the Iris 640 is supposed to be.

Thanks!