I have tested Nero for AC3 decoding and it seems that DRC isn't removed correctly. Here is
source,
AC3 (DRC: None),
AC3 (DRC: Speech). When comparing SNR of decoded files (I use CompAudio) Nero gets same SNR as libav on file encoded without DRC, but on second file Nero gets much worse SNR, while libav has nearly same numbers.
I'm not the only one who gets this issue, it was previously reported on another forum.