Rotom or Gengar in RenPlat?

I caught a misdreavous in eterna forest and now I'm wondering if it's better for me to go after gengar or rotom in old chateau, since both are guaranteed. My box looks like this right now. Can anyone help me decide?

I caught a misdreavous in eterna forest and now I'm wondering if it's better for me to go after gengar or rotom in old chateau, since both are guaranteed. My box looks like this right now. Can anyone help me decide?