That really depends on your vocal talent. There may be some songs that you can't handle, for example, "I Will Always Love you", to sing that song you really have to be in control of your voice, you have to be able to hit the notes necessary to sing it correctly. One of my favorite songs is "Lean on Me" by Bill Withers. I think it would be awesome to sing that at the Xfactor. It really sets a good mood. Best of luck to you when you audition, I really hope that you make it.