Originally Posted by
cova
Problem on CO is if there is 1 upgrade seat, the system will skip the two person PNR and then upgrade the next single person in line for upgrade. So there is a chance you could miss out - but the plus is you will be seated in the same cabin.
It is the same on UA.
As long as you don't mind the "system" splitting you up for seating allocations if stuff happens, I would go with separate PNR's, since I believe it enhances your chances of at least one of you (ahem, your wife

) of getting an upgrade.