What is one advantage of top-down assembly modeling? 

Top-down design is always faster and more efficient then bottom-up design. 

No in-context relations are needed, which can sometimes be difficult to manage in large projects. 

Each part file is a unique stand-alone model and no in-context relations are needed. 

Much less rework is needed when design changes occur. 

The parts know how to update themselves based on the way you created them.