I prefer 2.5" because it allows me to use the SSD in more ways. I put older SSDs or SSDs with too small a capacity into an external housing and use them for data backup or connect them to the Teleclub set-top box and use them as hard disk recorders.
To mirror the HDD, I recommend Macrium Reflect Free (64 bit). With this software you can mirror an HDD quickly and easily with the function "clone this disk".
http://www.chip.de/downloads...