Interesting question. I haven't ordered the bdp83 yet, but had the older Oppos and I've got a modded DV58AV. They're really close for DVD-A and SACD, but the Pioneer is far superior for RBCD. If you're only going to use them for Hi-Rez, then I'd say go with the Oppo and HDMI, under the assumption that it's unlikely that Oppo focused a lot of attention on RBCD performance. I could be wrong. I'll be able to answer in a while, but if you're trying to make a purchase decision right now, then I can't give you a risk free answer.
Generally, the hi-rez formats have much smaller performance gaps than low rez, like CD or mp3. Those lower rez formats really benefit from an upscaling routine and alogarythm to output to analog. Neither the Pioneer nor the Oppo are top of the heap for low rez formats.