Oppo has a comparison table that shows the 980H vs 981HD and 970HD
here. They claim the 981 is the best for PAL/NTSC conversion but don't really give any details.
I own the DV-981HD and have played the Region 0 PAL disc of Night on Earth and it looked great. It's the only PAL disc I own.
I don't know if this matters but the 981 can be used as a region free player. One of the commenters on Amazon.com said how to do it. You need to enter a 4 digit code and change it to region 0. I haven't tried it myself but may in the future.
If you want component out and/or support for 7.1 PCM/DSD. the 980 is probably what you want. Otherwise, the 981 is a fine choice. I use mine for DVDs, SACDs and DVD-As and I think it's great. I use the 5.1 analogue out to my aging receiver.
Jim