Two of the best performances on last night's "X Factor" couldn't have been any different -- with one singer tackling a song sung by not one but two great vocal powerhouses ... and the other doing a low-key version of an original song.

After singing a bizarre round of dance hits, the contestants were able to do a song of their choice. Melanie Amaro, who had already done an Adele song earlier, decided to take one two more divas -- by performing "When You Believe" from Whitney Houston and Mariah Carey.

It's not an easy song -- but Melanie, of course, killed it.

After her big vocals, Chris Rene stepped up with a routine that was almost the complete opposite, acoustically performing the cool and low-key song "Where Do We Go From Here," a song he wrote himself.

Simon Cowell said the performance could have been "stupidity or a stroke of genius," but conceded it "was a stroke of genius."

One singer is set to go home tonight, who do you think it'll be? Melanie, Chris, Josh Krajcik, Rachel Crow or Marcus Canty?

Our money's on Marcus.