Two of the things being compared in "Because I could not stop for Death—" by Emily Dickinson are life and death. The use of parallel structures in the poem is an essential element of the comparison.
The first element being compared is clothing. The white clothing that the female narrator is wearing on her journey is the same color as a burial shroud. A white garment of the type being described is used for several other important life transitions, including baptism, confirmation, and weddings, suggesting that Death is being portrayed as one of many life transitions of the path between birth and the immortality of the soul.
Next, the grave which ends of the journey is described in terms similar to a description of a house, as having both a roof and a cornice. Both the grave in which our body rests in death and the houses in which we live while alive are thus being seen as homes to our physical bodies.