XBench Scores:
MBP Iris 6100:
Quartz Graphics Test: 108.64
UI Test: 20.46
MBP w/ eGPU (GTX960)
Quartz Graphics Test: 31.22
UI Test: 5.20
One other thing I noticed after the update is that when connected to the eGPU, the on board Intel Iris graphics card is not listed under the About This Mac Overview. As you can see in the picture, it says the GTX960 is running the laptop's screen in addition to the two external monitors. Not sure if this is of any significance, but on Yosemite, the Iris graphics would always be listed as running the laptop's screen.