They are all the same size. Some rooms have had the daybed replaced with a desk--handy for the many business travelers who stay there due to the convention center.
The last time we stayed at the YC, we needed a room with a daybed. Unfortunately, the night we checked in, it was pretty late and there were none available until the next day. When we did move, the room size was exactly the same. The only difference in the furniture was that our first room had an arm chair where the daybed would normally be. The second room had a daybed, but no arm chair. There was a desk in both rooms.
Our room without a daybed was a corner room with a bank of windows where the daybed would have been. Obviously, this isn't always the case.
Since the refurbishment, our rooms have always a daybed and desk. Before the rooms were last redone, there was a small table and chairs, but no desk.