Impress-watch posted a review comparing XQD (2933x, 440MB/s), UHS-II SD (2000x, 300MB/s) and the currently fastest UHS-I (633x, 95MB/s) in D500.
http://dc.watch.impress.co.jp/docs/review/lexarxqd/1003928.html?utm_campaign=top_article&utm_medium=content-text&utm_source=dc.watch.impress.co.jpThey set D500 in the fast continuous shooting mode (10 frames/sec.). The result is:
Maximum amount of frames until the continuous shooting stops (frames, 14bit losslessly compressed RAW/RAW+JPEG fine):
XQD 200 (limited only by the camera spec)/108
UHS-II 102/38
UHS-I 37/26
Writing speed of 35 RAW/RAW+JPEG files:
XQD: too fast to measure/1.3 sec.
XQD (100 RAW/RAW+JPEG): too fast to measure/2.8 sec.
UHS-II: 2.0 sec./4.7 sec.
UHS-I: 12.2 sec./unable to shoot continuously
"Too fast to measure" means that they could only see the writing LED on D500 to light for several hundred "milliseconds" and they could start shooting immediately after, as if nothing had happened. It was so fast that they had no time to press the start button on the stop watch they used.
On the other hand, when they tested the mirroring mode using XQD and SD cards, the writing speed dropped drastically, as expected.
Frames they could shoot until the continuous shooting stops (RAW+JPEG):
XQD + UHS-II: 28
XQD+UHS-I: 25
RAW into XQD and JPEG fine into SD:
XQD + UHS-II: 58
XQD+UHS-I: 32
Hope this would be of any help.