Performance gain: nil.
You may win some synthetic benchmarks, but in actual usage, you will not be able to detect any difference.
Past that, how much performance you get out of the hyprid drives is hugely dependent on your access patterns and a bunch of other unknowable factors.
If you want storage performance buy a SSD; the bigger the better.
Reserve hard drive usage for storing large files like video's.
The hyprid drives do fit well in a laptop that needs lots of storage, and has the capacity for only one drive.