The Firecuda is an sshd and the barracuda is a hd , the sshd firecuda has 8gb of flash memory as well as a spinning hard disk. the barracuda is a normal hd no flash memory.
Technically the Firecuda should be faster, but only for frequently used files and you have zero control over what those files are.
I too thought of getting an SSHD for data storage but the difference was negligible when it came to data retrival.
If you are not using it for OS then save some money and get the Barracuda .
Hope this helps .