Other than the highlighted portion a cruise card provides the same exact information to Princess.
As far a asking for your cabin number, the waiter was only checking to make sure he was billing it to the correct person and not someone standing next to you. It's faster to ask rather than trying to match a face to the screen. During slow periods, they never ask.
I have yet to hear of just one reason why a medallion is worse than a cruise card after all this time of being used. If I missed something, please let us know.