The Spanish site,
mubis.es, has an article on the new restoration, illustrated with screencaps which you can slide between the 2010 and 2015 versions.
I'm prohibited from directly linking to other forums but once you enter the site, you'll see an image of Kirk Douglas with the heading,
Comparativo Espartaco. Immediately below the image, you'll see the heading,
Comparativa de Espartaco en Blu-ray. Click on that and it will take you to the article. Should the site get updated and the home page changed, search instead for
Espartaco.
The screencaps are a revelation.
PS @Noodles This might change your mind about upgrading your Digibook to the Steelbook.