Interestingly, some reframing, color, and contrast tweaks were done on certain shots in the DC. To try to keep things as fair as possible, I didn't include any of those in the comparison.
I don't believe the Warner version was "filtered" prior to encoding. Check the final pic. It's not representative of 95% of frames in that shot, but this one looks to me to have (very) slightly more grain in the Warner image.
Something happened to the horizontal resolution of Paramount's master. They both have lines as fine as one pixel high, but the Warner version also has lines that are only one pixel across. These are averaged out in the Paramount version, losing the incredibly tiny details. I guess they used different resize settings to prevent aliasing? (see image #17, the computer screen)
The chroma planes seem to be aligned slightly differently on each. Not sure if this is related to the above or not.
I'm also trying something new: I checked the extended BDInfo for each and found their largest single-frame size, and I've included those frames from both encodes. This represents a bitrate spike, so in theory they should be the most taxing frames efficiency-wise. In theory...Watchmen: Director's cut - United States - Warner - 18.48Mbps VC-1
Watchmen: Theatrical cut - United Kingdom, etc - Paramount - 27.02Mbps AVC
(click Stop on this thread to not waste time downloading from both servers)