After thinking about it, I would recommend reversing which is on emmc and which on SD. You will not be updating CM7 very often and likely updating CM9 a lot. It is easier to update emmc, so I would put CM9 on emmc and CM7 on SD.
Sent from my Nook Color running ICS and Tapatalk
See my Nook Color Tips Thread here
and my Nook Color EMMC Partition Repair Thread here
and my Nook Color Updated CM SD Installation Instructions here
and my Nook HD/HD+ stock tips thread here
and my Nook HD/HD+ CWM Root Tools thread here