16 BIT VERSUS 24 BIT

I'm a bit confused as to what the original question is but let's clear something up. "Bit rate" is technically incorrect terminology here. This refers to the aspect of data transfer rates done online let's say, such as with MP3's. Really we should use "Bit Depth" or "Word Length".
Of course higher bit depth is better and not only for dynamic range and more importantly better gain staging and headroom but also for DSP processes. The more processing the larger the number to represent the changes of those processes. The better representation the less disposition to error ["less" because there's always some kind of error].
 
In reality yes 24 bit is quieter, but is it actually worth 256 times more space for the audio files for a very small difference in noise, probably not.
I follow your logic for all but the space requirement. I assume you are referring to something else, but the data space requirement is a predictable 50% greater for 24bit vs. 16.
10 minutes @ 44.1/16 stereo is 103MB
10 minutes @ 44.1/24 stereo is 155MB