They are both pretty ugly, but I would say that the X1 looks slightly better.
I wonder if the PS4's slant has some function to it. The slant will prevent people from being able to slide it all the way against a wall, so the air vents can't get covered by someone who doesn't know to keep it ventilated.
Platinums: Red Dead Redemption, Killzone 2, LittleBigPlanet, Terminator Salvation, Uncharted 1, inFamous Second Son, Rocket League