@Seulbae The pixiv version that is the same in dimension but smaller in size is always the parent because it has better image compression.

zaregoto said:

The pixiv version that is the same in dimension but smaller in size is always the parent because it has better image compression.

However the file type of the pixiv version is jpg, the twitter is in png. Besides, the difference in the quality of both images are miniscule that 5 other users decided against uploading the pixiv versions, having a duplicate that is only a fraction better or worse than the other in my opinion is unnecessary.