I'm definitely in group B and I tell you the difference feels unreal to me, it's almost as if I was listening to completely different albums. The thing is group A wouldn't have noticed if the HDtracks master was also the CD master. They would have turned up the volume a bit more just like everyone else and enjoyed the album just the same or maybe even a little more with the better quality working its subconscious ways.
That's why it's sad separate versions even have to exist, because it wouldn't be necessary.
I had never heard of HDTracks before now, but I can tell you with 100% certainty that I will be buying all my albums from them in the future, if they are available on there. I've been listening to a FLAC CD rip up until now, and I can definitely hear a difference between that and the HDTracks FLAC files I just bought last night.
The keys are a little bit more noticeable, although still overall buried too much for my taste, especially compared to ADTOE where they were quite prominent. I'm disappointed about that, and I hope it reverts for the next album, however the drums definitely sound way better on the HDTracks version. They sound more up front in the mix overall, and the larger dynamic range makes all the hits come out much clearer.
Overall, it's just more clear in general, with no distortion or clipping in certain parts where there was in the CD mix. Plus, it's a digital download! I can actually buy the album and support the band, which I do want to do, and not have a physical disc that I don't want kicking around my house. Win, win.
I'm disappointed this is even an issue. Most people are going to listen to the CD, but this is the way it was meant to be heard. I agree with Nef 100%. There is simply no reason for there to be two separate mixes. I thought we were over this whole "loudness war" thing now that people were aware of it, but apparently the record labels are still idiots...