Emily will go in there because she slowed Toxic down which will split alot of people, and then she did a very Rock song (by The X Factor standards) in the second round that isn't even that well known to people, even though I actually liked it, it will go down the same way that Max Stone's Secret Garden did last series.
And in the last few series the performance of the night at the top 5 will also go into the bottom two on the night, Luke Friend with his Skinny Love in series 10, Lauren Platt with her Don't You Worry Child in series 11, and Lauren Murray ruling her night in series 12, so for me the other act that's in trouble because she overall was the strongest act at this top 5 is Saara.
So to put it in a more simple term, I think that the bottom two will be Emily vs Saara.