Any theories as to why a PAL DVD sounds better than a Blu-ray rip?

[FendersRule]

I have a rip of John Carpenter's Escape from New York on Blu-ray (it's 4GB in size). I typically buy all my movies flat out, but this transfer I was extremely unsure about due to the pictures online. It's probably, the worst Blu-ray transfer of all time, and I do not recommend purchasing it.

Anyhow, the rip looks to be an exact replica of what the Blu-ray actually is from what I've seen. I also have a PAL DVD of Escape from New York.

I am dumbfounded by what I actually found though:

Comparison:

Escape from New York PAL DVD (DD 5.1 AC3 480Kbp/s Audio), MPEG-2 video, played through XMBC from Xbox (TOSlink) and upscaled 720p. My modded Xbox is the only system that can play PAL stuff.

vs

Escape from New York Blu-ray .m2ts rip (DD 5.1 AC3 640Kbp/s Audio), Mpeg-4 video played through PS3 1080p.

Both systems are plugged into an Onkyo RC-160 receiver (PS3 = HDMI, Xbox = TOSlink). The Onkyo displays "Multichannel" for the PS3 (which means the PS3 is probably processing the signal?), and the Onkyo displays DD for the Xbox (which means the Onkyo is probably processing the signal).


Results:

PAL DVD had a more natural film look to it due less edge enhancement (the blacks weren't crushed, there were no halo effects). The resolution is of coarse a little lower, but honestly, the Blu-ray doesn't have much more of a shaper image due to the obvious transfer issues. ANYHOW:

The most important finding - THE DVD HAD BETTER SOUND! For some reason, the Blu-ray rip (AC3 DD 5.1 640 Kbp/s) had a much "flatter" sound, and the dynamics and depth just seemed rather dull compared to the PAL DVD (AC3 DD 5.1 480 Kbp/s). I did note that whenever I switched to the Xbox, I had to turn down my sound from "48" on the receiver to about "43".

I'm dumbfounded. Not only do I prefer the PAL DVDs video quality (slightly), but I heavily prefer the sound quality, even though it's running at a slightly lower bit rate.

Possible reasons:

(1) Something innate with the formats (maybe the Blu-ray rip suffered poor compression with the audio, even though it still runs at 640 Kbp/s). Or perhaps, maybe the lossy track on the Blu-ray really sucked....

(2) Something with the signal processing from the PS3 (something that a newer Bitstreaming PS3 can do better)?

(3) Others?