Indifferent to the match up and typing out a whole debate sounds exhausting. But I like to play devil's advocate so let's put forth a counter argument to Shiro winning. Also, the pictures do help
My fellow voraphiles, Shiro would be an ideal candidate for diaper filler. If she were packed behind some padding there would be more food and resources to go around. One less mouth to feed and one more hungry mouth filled. This young upstart genius could potentially have changed the world. The upper class can sit comfortably in their status knowing that such world changing potential has been spent filling a diaper.
Monsters can rejoice knowing that a lowly human has been put in their place and by one of their own no less, since surely a ghost counts as a monster. Shiro will be sent to meet her maker long before the world could tarnish her soul and would stand blameless and innocent before whichever god has dominion over her.
Mayori fans will rejoice that their poor, unfortunate ghostie finally has a win and Shiro fans will be unable to deny that she made the most adorable diaper filler. Ghost hunters will have a prime opportunity to observe a ghost in action as Shiro is consumed and digested before their eyes. While both girls are cute and hungry and would make any loli pred fans happy, Shiro is clearly the better choice for prey. Her cute little body would look delightful melted down and squeezed into a diaper, but Mayori has no body to digest. The ghost would come out as nothing more than a sad fart, leaving a depressingly empty diaper.
For the good of all, please vote Shiro for diaper filler.