I own the fatal1ty and upgraded from a cheap MSI board. From my experience I really enjoy the fatal1ty. I can't tell you much about the extreme9 but here are the differences:
Fatal1ty - 32GB
Extreme9 - 64GB
Max Memory Speed Support:
Fatal1ty - 2100 (oc) - 2100(OC) / 1866 / 1600 / 1333 / 1066 / 800
Extreme9 - 2450 (oc) - 2450(OC)/2100(OC)/1600/1333/1066 (notice 1866 isn't natively supported)
Fatal1ty - x2
Extreme9 - x8
Fatal1ty - 8 Channels
Extreme9 - 7.1 Channels
Fatal1ty - (3) PCI Express x16 / (2) PCI Express x1
Extreme9 - (4) PCI Express x16 / (1) PCI Express x1
I don't know why anyone would need 64GB of expandable ram, even 32GB.
I'm happy with the fatal1ty but they both seem very similar to me. The fatal1ty does have a dedicated mouse port and has some features that lend itself more to gaming - but both are high end boards. The extreme9 has more usb ports and has an intel LAN controller (which doesn't mean a lot).