For openers, the Apple Fusion drive is infact two distinct
and seperate drives (128 SSD + HDD). The Momentus has
16 gig flash integrated with the HDD.
The Momentus ends up making a best guess at what items
are accessed most often and puts them in the flash for faster
access.
The Fusion drive works in a similar manner, with much more space.
Check this http://support.apple.com/kb/HT5446.
With that said, whether your actual work files will end up in
flash space is likely an unknown, and therefor the faster drive
HDD part would be better.
Also, you want to grab a Momentus while still available as Seagate
has moved to their SSHD line which does incorporate more flash
but has gone with a slower HDD instead of the 7200.