At some point, perhaps during my navigator blog back in May I compared the two. FTTF’s benefits don’t have a value you can really attach, the key however, we can easily assign value to the specialty embarkation lunch, and WiFi we can as well. The key’s benefits provide diminishing returns based on the length of the sailing for two reasons; 1) its harder to amortize the value of the chops lunch, 2) you’ll have more time to do the “signature activities” and the special times hold less value.
If you are doing all carry on bags, dropping off the bags at the theatre is a great value, when we did the key the bags were already waiting for us when rooms were announced ready at 1pm. The room steward said to us that we were his key guests and he went and got the bags to have them ready.