Not true. MP3 quality is left to kbps and the encoder. They can reflect wave quality to the point there's no noticeable difference when correctly rendered. Vinyl is a lower quality than 44/16(can't remember what, but lower). So...an mp3 rip of vinyl may not be better than the real thing, but a digitally remastered mp3 of a recording originally on vinyl is more than likely going to sound better. Then, there's other factors to consider. If I rip an mp3 from vinyl to work with inside a DAW where I can process in a stereo 64 bit environment, i'm getting a better sound than o;d school vets who were running from vinyl to mono 8-12bit 11-22khz loops to have room on an old sampler that maxed out at like 1.2mb of sampling time.
Now, think about how great it would sound to sample an mp3 from itunes into a DAW in comparison to other outlets being discussed.