I took Michael Buble's 'Everything' and lined up to the sample of the FLAC/WAV to the MP3 and WMA. Invert the phase of the FLAC and add to the MP3 and then add to the WMA and save those files. The difference is not subtle. I will no longer be using MP3s in my car. I'm of the opinion that the difference file is the 'distortion' and the lower the better. I do not know if there is a better MP3 encoder than in Audition but it's what I've been using for the last 7 years.
or should we just bin this right away?
The purpose that might be served is that the OP would rethink the fatally flawed idea that difference signals, spectrograms, or any other visually or measurement-based metrics need have any correlation with perceptual quality, which obviously they do not.
I don't think that the OP is serious and just making a joke.
There has been quite a bit of MP3 S/N and negative comments about WMA files so...
Well, as an afterthought: they have, but the sense is quite the opposite: see how much we can throw away without actually noticing. So the more, the better!