Will depend entirely on either metadata or compression, if the two are found to be the exact same image. In terms of priority:
- Most metadata
- Best compression (no artifacts + low filesize)
- Least corrupted (no corrupted blocks or trailing data, etc)
- Ex. post #2566630, exact same image, but exiftool gives a warning:
Warning: [minor] Trailer data after PNG IEND chunk
Recently there's been a trend to reupload revisions but users should know not to just blindly upload new images if they're found to be worse (more artifacts and what not). I have slight fears that people will just upload blindly to take credit for those things -- there are some artists that make it a strange habit to introduce more artifacts in a replacement without any change.
So this new information is pretty much putting me, among other approvers, on high alert.
Updated by Mikaeri