Thebig differences came when I was copying files from the laptop to the card, a common thing you'd do if you want to play movies on your phone.As you can see in the chart below, the SanDisk Extreme and Lexar 633x cards were much faster than any of the competitors. The Galaxy Note 3's SD card speeds seem to max out at around 20MBps both reading and writing. Only the Extreme card hit both limits.

The SanDisk Extreme outperformed both the similarly-priced Leef Pro and the more expensive Lexar 633x, as well as slower SanDisk Mobile Ultra and Kingston Class 4 cards we were using to compare. The most intense video-recording use in mobile today is recording 30 frame per second, 4K video; the Mobile Extreme card had no trouble with that, either.

In most mobile use cases, sequential read and write speeds are a lot more important than random read and write speeds.Copying and playing photos, videos, and music all use sequential reads and writes, and that's what most people do with their microSD cards. Random reads and writes are more common when running an OS or application off the card, a much less common use. That said, the SanDisk Extreme card also had some of the best random read and write speeds in our group, both on the phone and on the laptop.