I heard a difference between the MP3 and wave versions, except I hated the wave version! I found it to be -worse- than the MP3. It was [cold], its musical life had been [erased] somehow. I would certainly not create a master from -this- version for pressing. It does not produce the same harmonics as the MP3 versions I downloaded (yes, plural. Long story short, I ended up comparing 4 copies of the MP3 vs. 1 of the WAV. file). I suggest something in the conditions was different when the WAV was produced, and there’s a lot lot more going on here than the FR graph or null test would indicate.
By the way, I came across this page because I was searching Google to find if people think there’s a difference between an MP3, and the converted WAV file created from that same MP3. Or more specifically, the disc you hear created from the MP3. Reason being, I just burned a disc from MP3 files, compared it to the original MP3s in Windows Media Player, and the improvement in quality from the CD is tremendous. Though I admit I did make an attempt to tweak the burn for better SQ.