Not really true, 1Gib/s link is able to saturate HDD speed (if we are still talking local) and as you probably want to make a clone either way you might as well

Not really true, 1Gib/s link is able to saturate HDD speed (if we are still talking local) and as you probably want to make a clone either way you might as well do it over network. 4x1Gib/s or 10Gib/s are more and more popular and in general local network latency is lower than HDD latency (surprising, isn't it). Sending over 1Gib/s network will be for sure faster than copying it on flash drive. Even if flash drive is able to do 128MiB/s speed, you have to first write it, swap machine, read it. Via network you do the write and read at the same time.