Originally Posted by SeattleDavid

At this distance I'd say go by the fewest MCE seats occupied - almost all of those flights on Dec 24 (if they exist on that date) will have some C space at some point, so being top of the list (is it still first come, first served until the end of the year? Or has the ordering of priorities already changed?).

Even if the priority order has already changed, I think choosing the flight with the least occupied MCE cabin and the least occupied J cabin (by seat map is easiest - any inherent inaccuracy in using a seat map is random - effectively equivalent - across all those flights) is your best strategy.