The study essentially proves that, at least in the workplace, any amount of NAND memory larger than 10GB would have a limited impact on performance. Of course, data-intensive tasks like analytics or video rendering, where fresh data is being accessed all the time, would benefit from larger amounts of faster memory, but an average user is unlikely to notice the difference between SSD and SSHD.

via Seagate: Hybrid Drives Don’t Need More Than 8GB Of NAND.