At higher bitrates, say 128kbps average and above, there's probably little difference.
If you're aiming at 64 to 96 kbps, various recent public listening tests show Vorbis AoTuV is probably a little better than Nero LC-AAC (or HE-AAC at 64k) but not quite as good as Apple Quicktime/iTunes/QAAC AAC encoder. The FhG AAC encoder supplied with WinAmp was beaten by QAAC CVBR mode in the 2011 96 kbps AAC test.
The new Opus codec is also statistically superior to all these at 64 kbps (and the 1.1 beta build improves its weakest samples in that test). At 96 kbps, it's much more marginal in some single-listener tests.
I meant to add that it's all dependent on the sample and the listener in question, so 'your mileage may vary', but the above are summaries of multi-user test results.
If you're aiming at 64 to 96 kbps, various recent public listening tests show Vorbis AoTuV is probably a little better than Nero LC-AAC (or HE-AAC at 64k) but not quite as good as Apple Quicktime/iTunes/QAAC AAC encoder. The FhG AAC encoder supplied with WinAmp was beaten by QAAC CVBR mode in the 2011 96 kbps AAC test.
The new Opus codec is also statistically superior to all these at 64 kbps (and the 1.1 beta build improves its weakest samples in that test). At 96 kbps, it's much more marginal in some single-listener tests.
I meant to add that it's all dependent on the sample and the listener in question, so 'your mileage may vary', but the above are summaries of multi-user test results.