Who actually decides what judges get what category?

[_Seth]

Probably a random team of experts and psychologists who've watched the show... but I dunno.

[Niamh.]

nah I bet Simon does, just acts like he doesn't!

[Callum]

Not sure but it's not done fairly. Cheryl's got a strong catergory three years in a row now, the producers obviously know giving her a good catergory will mean more airtime for her.

[Jack_]

The producers. As Callum said though, it's not done fairly at all.

[Tom4784]

Simon calls the shots oon everything else and he knows how to create drama and headlines so I'm guessing he chooses which judges gets each category.

[Crimson Dynamo]

They said on Xtra factor that Bill Oddie usually phones the decision in. Has done for years

[M X]

The producers, but I think Simon is part of it & just acts like he doesn't know.

[_Seth]

It doesn't make sense because X Factor is HIS show, he calls the shots... it must be what I suggested in the OP.