Looks like the PAL DVD is an NTSC-to-PAL transfer, and isn’t as sharp as a pure NTSC DVD.
The Japanese DVD is NTSC, and it looks to be a much better source than the PAL DVDs. And it has a much higher bitrate than the PAL DVDs, being over 1.6 GB bigger than the Australian DVD (which is the PAL 1990 cut but with just the English audio). And it’s also progressive scan, and not interlaced like the PAL DVDs.