You do not want to be modeling or drafting with a stylus.
What seems like a natural action is difficult to achieve repetitively because of the precision necessary. A mouse reilves the hand and can be parked.
I get this notion from extensively testing Wacom's Cintiq using Archicad and SketchUp with Cintiq's stylus. While this product is great for painting and drawing, it hurts the wrist to place elements. Pushing and clicking with a mouse is something that can be done all day - the alternative is an invitation to strain.
Dwight Atkinson