16GB MicroSD Class 10 / UHS Class 1

root@beaglebone:~# hdparm -tT /dev/mmcblk0

/dev/mmcblk0:
 Timing cached reads:   374 MB in  2.00 seconds = 186.97 MB/sec
 Timing buffered disk reads:  18 MB in  3.36 seconds =   5.36 MB/sec


BBB eMMC:

root@beaglebone:~# hdparm -tT /dev/mmcblk1

/dev/mmcblk1:
 Timing cached reads:   456 MB in  2.00 seconds = 227.79 MB/sec
 Timing buffered disk reads:  54 MB in  3.02 seconds =  17.91 MB/sec