After some non MB discussions and audio testing, I wanted to add a starting point for digital media. First, I talk here under the premise that MB is a music database with the end user, the music listener, as its target.
As it relates to FLAC files, which could be considered to encompass all variations of lossless media, I personally see no reason to have a separate release for a 16 bit FLAC and a 24 bit FLAC. This would be great for use in the idea of having release variations, but as far as the end listening user is concerned, and generally speaking, these are the same thing. In fact, one could make a point that the 24 bit FLAC is worse than the 16 bit FLAC, again with the use of listening to it in mind.
As it relates to iTunes and the Mastered for iTunes releases, I again see no reason to make those a separate release. I do however see it as important to specify the mastering engineers for the recordings as there is a mastering difference. This may cause issue though as there is no good way to indicate such things as it cannot be applied to the recording and there is no current method to assign relationships on the track level of a release. This again would be good as a variation vs a separate release.
The reasoning behind the notes above are actual differences in the product. The differences between a 16 and 24 bit FLAC are just not relevant to the listening user, and in fact, can actually sound worse for some for many reasons including sending audio in frequencies they are not designed to reproduce and forcing conversions to take place in order to reproduce the content. For the Mastered for iTunes case, this is somewhat meaningless as it relates to this portion. Yes, it is different than the standard iTunes, but what it is really doing is using a master that was mastered for its end product. This SHOULD have been done anyway, just like the master for vinyl and CD should be different. It is only a first phase in the end goal of having 24 bit audio on iTunes, but regardless, that 24 bit master is still ending in a lossy compressed M4A file. That is really a product improvement vs a new product.
I am a large supporter of adding more detail to digital releases, but even I cannot see the above examples worthy of separate releases. Not to mention I have recently personally tested a release in MP3, iTunes M4A, 16 bit FLAC and 24 bit FLAC. That said, it is hard to argue against actual results. I do want to again state that these files were used as-is, no modifications, as the intent is the differences to the end listening user.