The detail is from that last scaled version, and has not been rescaled again. The right side is from the Australian Blu-ray. This has not been scaled at all. Different applications were used to capture the two frames, so I am not comfortable comparing the colour between the two, merely the detail and sharpness. For visitors from NTSC lands, generally the PAL DVD is just a touch sharper than the NTSC DVD.

There really isn't all that much difference in actualy picture detail between the DVD and the Blu-ray in many scenes. Initially I selected this shot because I thought grabbing the detail around the group of mourners to the left of the screen would be revealing. In fact, there was hardly any difference (aside from the weird colour cast of the DVD. This shot shows a little more detail on the Blu-ray, but nothing to write home about:

Why the sky should be apricot on the DVD version is quite opaque to me. What I'm more interested in here is the lack of compression artefacts on the Blu-ray version, especially noticable about the ropes:

Those last two shots were from sections of the movie going back to Vito Corleone's origins. This next one is a 'present day' (ie. circa 1960) shot. Note that the colour cast is fairly similar between these two shots (although the BD is a bit brighter). Perhaps the apricot feel of the DVD shots above was inserted to create more of a reminiscent feeling. Anyway, for this present shot the is a touch more detail in Michael's (shiny, mafia-like) suit on Blu-ray, and you can almost perceive the gold-leaf writing on the spine of the book behind him on the Blu-ray, and the Blu-ray lacks the echoey ghost of the artificial sharpening on the DVD version (see the lighter borders around the window frame elements):

Just when I'm starting to thing that the improvements in the Blu-ray hardly warrant the additional expenditure, if you already have the DVD, I stumble across this shot, which changes everything:

In fact, that shot got me so excited I grabbed another detail to compare. Yes, the good old grass patch again. This really does separate DVD from Blu-ray. On the latter you can see where the grass has been worn, the different varieties which are struggling with each other, the variation in the height. And that water does look so much nicer too:

Back we flash to the past with Vito (and a very young Sonny), and back we flash to a nearly indistinguishable Blu-ray and DVD (except for the warmer glow of the former, and the elimination of some print dust):

Still back in the past with Vito, now we find that the DVD has a blue sky, while the Blu-ray has gone all apricot. How can you get more detail from the film, when it is clear that the graininess of the film means there is no more detail to be had: