Is it worth sacrificing concierge class benefits for a bigger 'family ocean view' cabin.
Yes, especially if more than two people are staying in the same cabin. Most passengers don't spend enough time in their cabins for the "concierge class" amenities to matter. The "family ocean view" cabin has additional lower berths, more storage lockers, and more "elbow room."
Depends entirely on where the CC is located.
If there are only 2 of you then you can get the best of both worlds with an AFT CC on the "M" Class ships.
Yes the Family Views are larger cabins and "some of them" have larger balconies than the AFT CCs but some FV have the same sized verandah/balcony as the AFT CCs.
I've read that Celebrity doesn't allow parties of less than 4 or 5 to book the FV until close to cruise time if they are not already taken.