There are many benefits of a floor-to-ceiling bathroom mirror, particularly behind the vanity. Large bathroom mirrors can be an instant way to change the shape and dimensions of a room. Because it extends to the floor, it can also make the space under a cabinet feel lighter and less dense, which is great for small spaces. Full-length mirrors also maximize the light in a darker bathroom, particularly great if natural light is limited and you want to make the most of it. The continuation of the unbroken vertical lines will also make the room seem higher and more vast. These mirrors are also great for functionality since you can get a larger mirror view head to toe when getting ready. They are also great for behind sinks and vanities two people use at once.
As Emily Henderson mentions, full-wall mirrors are often found in more contemporary and sleek spaces, making many reticent to use them in other bathroom design aesthetics, where they can seem out of place or too severe in their lines. They are often more difficult to keep clean and can suffer more moisture damage, chipping, and cracking than smaller mirrors. In addition, the lack of a frame immediately looks more contemporary, while homes with more traditional, farmhouse, and rustic-style bathrooms usually use framed mirrors as a design element.