The style of the mirror should be based on the style of the room. In particular, it should match the furniture already in place. A modern mirror should not be in a rustic room!
In the living room, opt for a mirror with a strong design. Here the functional side is not the most important. It will be an integral part of your decoration.
In the bedroom or the entrance, a full-length mirror will allow you to check your outfit before going out.
In bathrooms which are traditionally small, opt for a larger mirror to give maximum light reflection and depth to the room.