Debian Testing is currently making use of the Linux 4.8 kernel, GNOME Shell 3.22.2 as the default desktop environment, xf86-video-modesetting as the DDX over xf86-video-intel, X.Org Server 1.19.0, and Mesa 13.0.1.
I compared the current Debian Testing performance ahead of Debian 9.0 Stretch on this NUC6i7KYK with a Core i7 6770HQ processor integrating Iris Pro Graphics 580, 32GB of DDR4 memory, and a 500GB Samsung 950 PRO NVMe SSD.
For the most part Debian 9 performs right in line with the other Mesa 13-using Linux distributions.
No big surprises with Debian not using any aggressive optimized defaults, etc.
You can explore more of this New Year's Eve Linux benchmarking data via this OpenBenchmarking.org result file.