You may have misinterpreted my speed test. The microSD card is capable of much higher speeds than the router is capable of. It is capable of 60+ Mbps transfers on my PC, but only 13-15Mbps Read/5-6Mbps Write transfers from/to the router. Personally, I like the Kingston Canvas SD cards, but Lexar and Sandisk are also good, as long as you choose those with higher speed ratings. In particular, check the Write speeds because many SD cards have fast Read speeds, but much lower Write speeds.

My intention of the microSD card in the router is only to store/stream movies and to access miscellaneous files for travelling. Also, I can do backups of photos (jpeg, raw) wirelessly. The relatively slow speeds are adequate for my purpose, but definitely the router cannot act as a general purpose NAS storage device.