Digital wall clocks will typically use either LCD or LED technology in order to display the time, with LED being the most common. The difference between LCD and LED are as follows:
LCD: LCD stands for liquid crystal display. They have two layers of glass which are polarized before being assembled together. Liquid crystals in the screen either pass or block light to create the display. LCD screens are lit from the back of the screen with fluorescent lamps.
LED: A LED screen is actually a type of LCD screen. Instead of fluorescent lamps, LEDs use light emitting diodes (LED). It generally consumes less power and the back-lighting is available in two types: edge lighting and full lighting, which doesn’t make much of a difference for your clock, though your TV might have something else to say about it.
If you want a super simple digital wall clock, then both LCD or LED should be just fine for your tastes. If you care about the specs and you want a more extravagant clock, then LED offers a better visual experience for users.