I know this is splitting hairs a little bit, but the 980 is generally considered "better" than the 981 in terms of audio.
Differences (taken straight off the www.oppodigital.com
website):980 Audio Features not on the 981
- Direct Stream Digital (DSD) over HDMI (Requires compatible A/V receiver)
- Individual analog 7.1-channel surround outputs, compatible with 5.1-channel and down-mixed stereo [981 only has 5.1 compatibility
- Dolby Digital Surround EX decoding
- Built-in lip sync (audio delay) function981 Audio Features not on the 980
- 3D Surround (Virtual Surround): Concert, Live, Dance, Techno, Classic, Soft
There may be other slight differences as well, beyond the fact that the 981 has superior video processing compared to the 980.
I'm not sure if any of these functionalities will affect the performance of your system specifically, but I thought the differences were worth pointing out.