Personally, I think this has a lot to do with the "purpose" of the room..ie..in a Control room, the ceiling is one of the "early reflection" points over the engineering seat, which needs broadband absorption. In this case, a plain ceiling is a problem. And "usually", the console blocks reflections from the floor at that location.
As to a recording room, again, I think a hard floor surface helps maintain HF ambiance, while broadband ceiling absorption helps eliminate comb filtering, as a mic is closer to a standard residential 8' ceiling height than it is to the floor. I'd suggest just use a 4'x4' piece of 3/4" MDF/PLY or whatever under a vocal mic and a couple of 4x8 sheets under drums.
One more thing. On a side note, I'd suggest another little idea, even if it hasn't been "scientifically" tested..at least that I know of. This comes from 2 different experiences and one PRO CR studio example..Apple studio CR in London. This has to do with making the middle area of the room a hard surface, and the perimeter of the room, carpet. Say..24" wide strip around the room. I used this idea in my own CR. The perimeter is a 24" wide strip of carpet, and the middle is Laminate. A friend of mine did the same in his live room, only using Linoleum in the middle. It really made a sonic difference in the room..vs all hard or all carpet. All I know is it sounds great..even without other treatments. I can't exactly define what I hear, but I asked about this on an acoustics forum one time, and one of the "experts" claimed that because of "diffraction" at the edge of the two surfaces, an "impedance difference" exists which causes a +1 absorption coeffiecent at this area of the carpet, even when there is no height difference...meaning you get extra LF absorption as a benefit. Whether this is true or not, I can't prove..but my ears tell me something is gained from this technique. Although, knowing that LF's terminate in ALL corners of a room..ie..FLOOR/WALL, this tells my belly something must happen between the hard floor surface, the wall hard surface, and the carpet between. And as a side note...not long ago, I saw a picture of one of Apple Studios CR's and sure enough...they used this technique, although their room is quite large, and the perimeter strip of carpet was about 4-6' wide, and actually varied as the edge was curved back and forth. Which makes sense to me, as the width of diffraction would vary too...ie...diffusion! My friend did the same..ie..curved edges. Again though, I have no empirical proof of anything here. Just a gut feeling. Anyway, good luck with your decisions.