The 5-piece door is more complex but more reliable and more pleasing in appearance. This is especially true with Mitered doors which offer more moulding choices than Cope and Stick designs.
The five pieces in a Cope and Stick door are the four parts of the frame, called Stiles and Rails. The Stiles are the vertical pieces, or sides of the frame, and the Rails are the top and bottom pieces. The fifth piece of the 5-piece door is the panel, which the frame surrounds.