Those aren’t 20% slower for the write speed though. The write speed isn’t stated until the questions part which says 250MB/s read speed and 90MB/s write speed (also on
their website). In camera they would be no better than the SanDisk extreme pro 90MB/s cards. It’s the write speed that’s most important for in camera use. Copying from the camera to the computer would be faster than the SanDisk extreme pro 90 MB/s but only if you have a UHS-II card reader.
There is not much point buying the cheaper UHS-II cards as they aren’t much better for write speeds than the 90 MB/s SanDisk cards. Sadly the fast UHS-II cards are very expensive and are needed for these high performing cameras.
The Lexar equivalents would be the Lexar 2000x 300MB/s read 260MB/s write but they are nearly £180 for a 128GB. You can see why the Manfrottos are tempting while they are currently half the price of the equivalent competition.