Well, received the Extreme Plus and ran a few tests. I picked 2 mp4 files with total size of about 3.3GB located on an external USB 2.0 drive connected to the SP2's USB port. First I copied the 2 mp4 files to the internal drive of the SP2. Then I copied to the SanDisk Ultra microSD card in the SP2. Finally I copied to the SanDisk Extreme Plus microSD card in the SP2. Both SD cards formatted with exFAT. Here are the average times for 2 runs each recorded:
Internal drive: 1:44 (minutes:secs)
SanDisk Ultra: 16:39
SanDisk Extreme Plus: 1:45
I suspected the Ultra card was defective when I posted the first post in this thread. In addition to the extraordinary slow write performance, both mp4 files were corrupted too. I'd been having other corruption issues with this card so it was good to document this versus the Extreme Plus. No corruption for the Extreme Plus. The Ultra's are supposed to be 30MB/s and the Extreme Plus 80MB/s, but clearly the Ultra in this case wasn't even close.
In a 2nd set of tests, I copied 162 image files totaling about 4GB to the same 3 targets as in the first tests. Here are the average times for 2 runs:
Internal drive: 1:43
Ultra: Failed to finish due to file or folder corruption both times
Extreme Plus: 1:53
Bottom line: The biggest surprise was the speed of the Extreme Plus card. Almost as fast as the internal drive. Benjitek, you were really right, they are blazing fast. Thanks!