Hey Dr
Rip speed is capped at 8x, and the High Bitrate Encoders (aacPlus / HE-AAC) are unavailable - the HE-ACC Encoders in free edition are capped at 128kbps. LA-AAC is capped at 256kbps.
Nero (
http://www.nero.com/eng/technologies-aac-codec.html), for example, has switches to set quality versus bitrate. Agreed: sounds like it's down to the aacPlus codec implementation.