Just the facts. In Lexar USB3 card readers with Xbench:
read (max): 84Mb / s
write (max): 37MB / s
in my EOS 650D according Magic lantern benchmark:
write (max): 32MB / s!
Unfortunately, this is far from the promised 60MB / s (I had hoped for stable 40).
For 128GB still are 39 unbeatable!