Kaeya or Rosaria?

Hello amazing Mavuika fans! First post here, as I've unfortunately lost my 50/50 for Mavuika but managed to pull through, I don't have enough to get Citlali. However with Xilonen which I have, I would like to know if Rosaria or Kaeya would be a better pick for a Mavuika, and if one or the other, how should I build them? Such as EM/ER requirements. Any feedback is appreciated!