The music on the Windows version comes in two types: 22kHz or 44kHz mp3s (you choose the quality in the settings). I haven't compared but I wouldn't think the PS2 version would have anything better than that. I believe that comment refers to the video and voice. As for iMuse, I can't determine that from the data but I'm happy believe what others say about it.
Updates on video:
The Windows videos are
all in bink format but most have them have a SMUSH header - if I remove this the bink player is happy with it. Also, the PS2 video is not cut off at the bottom as I said earlier but simply squished a little (which is trivial to fix when recompressing with bink). It also has 48kHz uncompressed audio, compared to 22kHz bink audio in the Windows version. It does sound nicer
After a struggle I managed to convert the PS2 video to and put it into the Windows version. The result is reasonable though for some reason the audio had to be reduced to 30kHz because the bink compressor didn't like it any higher than that. I'm happy to write up detailed instructions if anyone wants it.
More interestingly though, I've discovered you can set a flag in the bink videos to make them play at double size. Go 36 bytes from the start of the bik header and change 0x00000000 to 0x00000040. If you've patched your exe to set the resolution to 1280x960 (or higher, but 1280x960 is best for the backgrounds and things) then this is really great
. The subtitles stay in their original location, which looks a bit odd, but if you really want you can disable them completely by removing the smush header (seems disabling subtitles in the settings makes the video not play at all on current versions of windows).