If you are looking at the OS less devices that allow you to put an HD into each ot two connectors and do an A/B clone, then this is valid.
There are several scenarios for legal cloning....
If you want to use it as a disaster recovery device, you don't care so much about speed as accuracy. If you have a hard disk which is rapidly deteriorating, you may only have one shot to make a clone on another disk. The advantage of these devices is that they don't boot off an OS on the HDD, so if your corruption is due to a bad kernel or virus or whatever, you don't rely on it.
This by the way is what computer foresenics groups do - first step transfer everything to another disk via one of these cloning devices so that you retain the original and can explore the clone without fear or destroying the original.
On the other hand, if you are a big company and you want to create a standard image for your new PC deployment, (having entreprise licenses for everything and standardized PC), all you really care about is speed. There are devices will will allow you to clone several disks at once from one master.
I haven't used either of the models you mention.
James