Outward appearances are definitely deceiving when it comes to LCD and Plasma televisions. Although both types of televisions are flat and thin, they employ different technology in an attempt to deliver similar results.
Plasma TV Overview
Plasma television technology is based loosely on the fluorescent light bulb. The display itself consists of cells. Within each cell two glass panels are separated by a narrow gap in which neon-xenon gas is injected and sealed in plasma form during the manufacturing process. The gas is electrically charged at specific intervals when the Plasma set is in use. The charged gas then strikes red, green, and blue phosphors, thus creating a television image. Each group of red, green, and blue phosphors is called a pixel (picture element).
Although Plasma television technology eliminate the need for the bulky picture tube and electron beam scanning of traditional televisions, because it still employs the burning of phosphors to generate an image, Plasma televisions still suffer from some of the drawbacks of traditional televisions, such as heat generation and screen-burn of static images.
LCD TV Overview
LCD televisions, on the other hand, use a different technology (see also question #1 for this same explanation).
Basically, LCD panels are made of two layers of transparent material, which are polarized, and are "glued" together. One of the layers is coated with a special polymer that holds the individual liquid crystals. Current is then passed through individual crystals, which allow the crystals to pass or block light to create images. LCD crystals do not produce their own light, so an external light source, such as florescent bulb is needed for the image created by the LCD to become visible to the viewer.
Unlike standard CRT and Plasma televisions, since there are no phosphors that light up, less power is needed for operation and the light source in an LCD television generates less heat than a Plasma or traditional television. Also, because of the nature of LCD technology, there is no radiation emitted from the screen itself.
Plasma vs LCD
The ADVANTAGES of Plasma over LCD are:
1. Larger screen size availability.
2. Better contrast ratio and ability to render deeper blacks.
3. Better color accuracy and saturation.
4. Better motion tracking (little or no motion lag in fast moving images).
The DISADVANTAGES of Plasma vs LCD include:
1. Plasma TVs are more susceptible to burn-in of static images.
2. Plasma TVs generate more heat than LCDs, due to the need to light of phosphors to create the images.
3. Does not perform as well at higher altitudes.
4. Potentially shorter display life span - this used to be the case. Early Plasmas had 30,000 hours or 8 hrs of viewing a day for 9 years, which was less than LCD. However, screen life span has now improved and 60,000 hour life span rating are now common, with some sets rated as high as 100,000 hours, due to technology improvements.
LCD television ADVANTAGES over Plasma include:
1. No burn-in of static images.
2. Cooler running temperature.
3. No high altitude use issues.
4. Increased image brightness over Plasma.
5. Lighter weight (when comparing same screen sizes) than Plasma counterparts.
6. Longer display life used to be a factor, but now LCD and Plasma sets both have at least 60,000 hour or higher lifespans.
DISADVANTAGES of LCD vs Plasma televisions include:
1. Lower contrast ratio, not as good rendering deep blacks.
2. Not as good at tracking motion (fast moving objects may exhibit lag artifacts) - However, this is improving with the recent implementation of 120Hz screen refresh rates and 240Hz processing
in higher-end LCD sets.
3. Not as common in large screen sizes above 42-inches as Plasma. However, the number is growing fast, with 46 and 47-inch screen sizes becoming more common, and some LCD sets having a screen size as large as 65-inches also available to the general public.
4. Although LCD televisions do not suffer from burn-in susceptibility, it is possible that individual pixels on an LCD televisions can burn out, causing small, visible, black or white dots to appear on the screen. Individual pixels cannot be repaired, the whole screen would need to be replaced at that point, if the individual pixel burnout becomes annoying to you.
5. LCD televisions are typically more expensive than equivalent-sized Plasma televisions (although this is changing), especially when comparing EDTV Plasmas to HDTV-LCD Televisions.
For a more detailed look at the LCD and Plasma comparison, check out: Should I Buy an LCD or Plasma Television?