You are comparing "Momentus" a hybrid drive with "Fusion Drive" a tiered storage solution. Fusion Drive gives you a giant, huge SSD drive compared to Momentus'

You are comparing "Momentus" a hybrid drive with "Fusion Drive" a tiered storage solution. Fusion Drive gives you a giant, huge SSD drive compared to Momentus' on-drive flash. We are talking about orders of magnitude in difference in flash size. There are several reasons why OS integration could yield better performance. Notably, an understanding of what happens at boot time. While the machine is running, stuff useful for boot may not be used again. However, the OS can signal to the tiered storage "hey, we are shutting down. prepare the SSD so it will be fast for boot!". The scenarios are endless. We could talk about hibernation, etc.