After the news that all Lexar memory cards will be discontinued, there have been some discussions about the speed of the different SD and XQD memory cards. I found some tests performed by Lexar that you may find interesting – the first one is a comparison between the Lexar 64GB 2000x SDXC UHS-II ($94.82) and Lexar 64GB 633x SDXC UHS-I ($26.95) on a Nikon D7500 camera:
https://www.youtube.com/watch?v=a-7-YThsRBQ
Here is a similar test performed on the Nikon D500:
https://www.youtube.com/watch?v=6xp-asz2Qxc&t=15s
and finally the Lexar 64GB 2933x XQD 2.0 ($89.49) vs. Lexar 64GB 2000x SDXC UHS-II ($94.82) comparison test on the Nikon D500:
https://www.youtube.com/watch?v=DDTRs2jUSHk&t=15s
More memory card speed tests can be found here.
Lexar memory cards are still available for sale at B&H, Adorama and Amazon.
Update: additional memory card tests can be found here.