First of all, it's wrong to assume that just because the bitrate is lower, that the encode is worse, the encoding tools change and improve with time, and we do not know if the tools remained the same between these.
That being said, just going through some of these, the BD looks sharper and preserves more grain, but there is more blocking as well, see particularly #2 in the upper left the blurry bricks in the background, there are a few that are slightly brighter, on the HD-DVD they remain blurred grainy bricks in the background, on the BD they turn into blocks. Also look at her right collar (your left) and her right shoulder (your left), see how on the BD it gets blocky, and on her shoulder where there are the strands of hair it gets all flat and the hair gets blurry. This is interesting because they are both I frames, according to the caption, and the filesize for the BD frame is larger than the HDDVD frame, but look at the blocking!
But then look at image #4, that looks significantly
better on the BD, all the grain isn't washed away, look at all the detail on her coat and her belt particularly, that all gets lost on the HD-DVD, but they are not comparable frame types and the BD framesize on that one is larger than the HD-DVD.
Same with #5, no comparison, different frametype, BD frame way larger, way better.
#6 they look very similar, maybe a slight and insignificant sharpness advantage to the BD, but I'd say they look more identical than anything.
#7 is completely identical, literally. In fact it makes me doubt the caption on those images, those two are the exact same image, at least to my eyes.
#8 is a mixed bag, the blurry parts look more detailed in the grain/noise with the HD-DVD, but the fine lines on the stone looks more detailed on the BD. I don't really see any blocking on either though, not much detail to see.
#9. Look to the left of his hat. Wow, blockiness to the nines on the BD, HD-DVD while less detailed on his face, doesn't have all that macroblocking, and that's an I frame on the BD even.
#10 comparing P and B, they look more similar than anything
But #11, comparing I and I frames, BD mops the floor with the HD-DVD.
So really, all I see here is that yes they did a different encode, but it's a mixed bag in terms of results.
The purpose of this thread is to try to identify all of the Warner VC-1 encodes that are different/"new" on the Blu-ray vs the HD DVD and compare them. (And to discuss why the hell they would do such a thing without increasing the average bitrate...)
I just want to point out that if there isn't a need to increase the average bitrate, then there's nothing to be gained by doing so. It looks like there could have been some gains on this title on both the HD-DVD and the BD encode. But just assuming that an encode that is higher bitrate is better and an encode with lower bitrate is worse is far too broad a generalization, and is not necessarily true, particularly if the encoding tools used are different, and also there is the skill of the person(s) involved actually doing the encoding.
We can make very broad statements about encodes that are significantly higher bitrate, of the same codec, using similar or the same tools, but if the difference is small, it's not a safe conclusion to jump to that the lower bitrate one must be worse.