If you are staying in a standard room on the 14th floor you have a good chance of getting a Magic Kingdom view. There are only 5 standard rooms on that floor and 4 of them are on the MK side. There are two king rooms that both face the Magic Kingdom. There are 3 rooms with queen beds and only one of those is a Bay Lake view.
One thing to consider is that even if you happen to get a room on the Bay Lake side, the concierge lounge has a beautiful view of the Magic Kingdom. The balcony even has tables for you to sit and enjoy the view.
The 12th and 14th Floors do both provide identical service now, but they provide different experiences. If you enjoy the feel of the open tower and want to be able to walk out of your room and hear the concourse, Chef Mickey's, and the monorail then the 12th floor is probably your best bet. Another consideration is that the 12th floor has a brand new lounge.
The 14th floor is kind of sealed off from the rest of the resort and has a very intimate feeling to it. It doesn't have the interior corridors / balconies that over look the concourse so it is very quiet. That can be a plus or a minus depending on your personal preference. I really enjoyed how quiet and relaxing it felt. There are only the 5 rooms and 11 suites, so it seemed the attention was very personalized. The desk staff greeted us by name every time we boarded or disembarked the elevator and remembered what park or restaurant we doing that day.
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