V9 is just being recommended by whoever it is that is explaining how to use it through an ISO that you've strapped FMCB to boot from
V10 probably has more codes and works the same it's just that most of the in-depth tutorials out there are using V9 in their tutorials.
I've used FMCB+CBv9 with ISOs before and the outcome was always 50/50 it breaks some games or makes cause for additional removal of padded dummy files and sometimes the game works fine with nothing required after merging said tools to ISO