Take a look at my N30 announcement thread, particularly the first post.
There are comparative light measurements and photos of the N30, X990 and numerous other lights.
The N30 is significantly lighter weight and more compact.
The X990 is heavier, but has an adustable beam and an adjustable head.
They are nearly identical in throw.
They also put out almost the same amount of light over all.
The X990 throws more of it's light down field in it's larger corona.
The N30 has a wider and brighter spill.
The photos in the post will help all of this make sense.