Going with Mob here for one big reason,
Perona's main fighting style just buffs the kid. Shigeo's body has been shown to quickly and rapidly react to such attacks which would cause serious problems for Perona.
For starters, how would he find her? She has to project his ghosts to him, his spiritual sensing would indicate which direction they are coming from (Perona doesn't really hide her ghosts like that at far ranges) and SBA indicates that Mob knows her general starting direction. As an added bonus Mob might not even need to find Perona in the first place due to his mental reflection ability. Perona mentally links with her ghosts in-character which means she'd be very vulnerable if Mob unleashed any mental assaults back on her instinctually, which while normally could lead to a draw as both go unconscious it instead would be a Mob win as Perona's effects go away once she's knocked out.
Secondly, the physical fight. Persona doesn't really fight on a physical level and almost exclusively goes for depression attacks. While the ghosts are faster, the moment Mob starts absorbing energy they are going to end up being a non-factor as his peak shields will just be absorbing their energy giving him stronger power. Perona's best bet is to just take Mob down in a physical sense before he has time to ramp up, but since this is Perona that isn't really happening.
Lastly, the Stomp Factor.
REIGEN ARATAKA! This is one of Reigen's
special techniques where he uses his
social influence to
incapacitate a girl before Mob
accidentally kills her. Perona, who was scared straight by someone immune to her hollows powers, fled Thriller Bark immediately in hopes to not have to fight the strongest psychic in the world. (Reigen was trying to hide from the zombies, but wound up walking directly into Perona's path on accident)