The pencil drawings always have a level of crispness of 
detail that get lost in the cels. One aspect where cels 
can really degrade artistic quality is the trace lines.
With the pencil, animators can adjust the thickness of the
lines they draw.  
Of course, when the drawings get traced onto cels, the lines
degrade to a similar thickness. The thick, darker lines tend
to bring things out towards you more while the thin, light
lines provide a real sense of detail and delicateness.

Looking at various drawings in my art class, it's very 
obvious that reducing a work's lines to the same thickness
takes something away. 

I hope you'll show everyone your MKRE gengas when they come!