That's because they're opposites in presentation. The X1 is bass oriented with a slight tilt in treble at 10khz. The MA900 is midbass/mids oriented, with rolled off sub bass and downward sloped treble.
I don't like comparing two headphones with very different presentations. Apples to oranges.
I know but it's hard to decide :D
I might consider the X1 too...
I really dunno right now... I'll get the MA900 first and will see... But the X1 does seem tempting :]