USB 3.0 - 16Gb
RPi3:~ # hdparm -t /dev/sda1
/dev/sda1:
Timing buffered disk reads: 116 MB in 3.01 seconds = 38.60 MB/sec
RPi3:~ # dd if=/dev/zero of=/storage/test bs=8k count=50k && sync; rm -f /storage/test
51200+0 records in
51200+0 records out
419430400 bytes (400.0MB) copied, 17.259372 seconds, 23.2MB/s
Other USB 3.0 - 16Gb
RPi3:~ # hdparm -t /dev/sdb1
/dev/sdb1:
Timing buffered disk reads: 122 MB in 3.02 seconds = 40.40 MB/sec