Short castling if my advantage is a time advantage, long castling if my advantage is a space advantage, no castling (as Black) if my advantage is a locked center and strong counterplay on the flanks with time compensation for White's space advantage. In general, anyways.
Short castling or long castling?
Sort:
Short castling is generally better: can be done 1 move sooner, does not require a premature queen move, the king is safer on the g-file than on the c-file.
Long castling is applicable when you want to attack h4-h5 supported by Rh1 or g4-g5 supported by Rg1.
For the openings you play, what way do you prefer to castle?