Reference, why I like ogg over all, smaller and better sound. That said,
'For low bitrates, WMA seems to be a better compression scheme than MP3. But the difference is not as huge as Microsoft would like us to believe.'
'Those parameters are selected to try maximizing quality and to reach the same filesize as the WMA samples, because the WMA samples are always bigger than the MP3 samples encoded using the same target bitrate.'
Of course, when MS does a study 'We could argue that the test samples could be carefully choosen in order to provide good quality with WMA and bad quality with MP3. But as there is no clue about this, we are ignoring this possibility, even if it is likely to be the case.'
So I would not believe what MS has to say at face value.
'It seems that at every bit rate tested the MP3 audio file comes out smaller, but only slightly.'
'It comes as no great surprise that WMA beats MP3 in terms of audio quality,'
But, that is with older MP3 encoders.
The rock solid conclusion that I can come to is try encoding both with the latest encoders, see which one sounds best to you.