When playing Blu-ray discs, Blu-ray players provide much higher bitrates over their lossy RCA or optical digital connections than are available on DVDs. Many people claim to be unable to hear any difference between the high-bitrate lossy audio and lossless audio.
The Oppo BDP-83SE has significantly higher quality multichannel analog audio connections than the standard version of that player.
Note that the Oppo 80 and 83 players also support SACD and DVD-A, which the Panasonic players do not.