The Platinum Edition of The Little Mermaid supposedly has issues with ink lines being thinned (possibly by the degraining algorithm?)
This image is kind of compressed and badly resized, but look at the comparison.
But in other instances, more ink line detail shows up in the Platinum transfer. Lighting effects also seem to be more "blown out" in the old transfer, not sure whether or not that's theatrically accurate? We know from Pinocchio and BATB (and the lightsabers in the 2004 ESB/ROTJ) that high-contrast lighting effects are sometimes dulled or flattened in modern transfers.
Steve Worth claims that in the modern BD transfer of Alice in Wonderland, double exposures, ripple glass effects and other effects animation are digitally ruined or replaced. He also says optical fades were altered, characters were separated from and regraded separately from the backgrounds, and the backgrounds were digitally frozen in place and lack any film weave.
In fact, Mr. Worth insists that many modern transfers of classic Disney animation have radically altered colors and all sorts of Lucasian digital alterations, rather than just being scanned, regraded and degrained. He said the same thing about Bambi. (In that case, he says every release since 1997 has some kind of digital alterations - in which case, the 1990 VHS/laserdisc would be the only straight film transfer.)
The BD of Dumbo has a couple bizarre color changes:
Notice that the three guys on the right have absolutely no line detail. It looks like they just laid a solid color mask over their uniforms. I have no idea why this was done.
Also, I thought I still had Molly's Cinderella preservation on my external hard drive, but it turns out I deleted it after I burned my copy.