A lumen is a unit of measurement of the luminous flux emitted by the projector’s internal lamp. The higher it is, the more the image will be visible in bright environments. Conversely, a low Lumen device will need complete darkness to project a highly visible image. The choice, in this case, depends a lot on the use you will make of the projector. If you need it for presentations in offices that are difficult to darken, then you may prefer a device with a high Lumen value. If you have to use it primarily at home, however, you could also save some money by opting for a projector with a lower lumen value.