It's completely unfair, first off, to make any U.S. X Factor / U.K. X Factor comparisons here. The former is just getting its live shows started, while the latter is well into them. The former just came to the States; the latter's been in the U.K. for yonks. The former is just getting its slate of performers started; the latter's had Katy Perry, Cher Lloyd (it's the U.K., she's a bigger deal there) and lots of others.
With all that said, as gets go, Lady Gaga > Outasight. (Sorry, Outasight. Keep on carpet-bombing commercials. Gaga had her guesting-on-Wale-songs phase of her career too.) Gaga will perform "Marry the Night" on Nov. 13--her second stint, following a "Bad Romance" performance in 2010. We also know that the performance is rumored to be "typically theatrical." At what point does a rumor lean so far toward accepted fact of the universe that it might as well be truth? Stay tuned for rumors that Gaga will play the piano and maybe sing a bit!