LCD vs Plasma
Among various flat-panel display technologies available, the two most popular are LCD and Plasma.
Minimum achievable pixel size is smaller for LCD, therefore minimum size of achievable Full HD LCD HDTV is smaller than that for plasma. This becomes a consideration for small rooms and/or short viewing distances.
 Screen Size (Diagonal Length)
Also consider LCD vs LED before taking the plunge on this type of purchase
 Plasma screens are limited on the low end by minimum pixel size that can be manufactured. Plasma screens are limited on the high end side by maximum power consumption and heat dissipation that may be considered acceptable. The demand for higher resolutions is chipping away at the smallest plasmas while the demand for green ( energy efficient ) products is chipping away at the biggest plasmas. For this reason the plasma was headed straight for extinction before the introduction of 3D television. Fortunately for plasma 3D television favors plasma over LCD and this is causing a resurgence of the plasma technology.
LCD screens can be manufactured in virtually any size. The probability of the panel having a defect however is proportional to its surface area which puts a practical limit on the size of LCD panel that that is economically viable at any given time. As the technology improves and defects become more rare bigger panels become economically viable.
Plasma thickness is limited by the glass that is strong enough to withstand vacuum and by the cabinet that is strong enough to support the glass.
LCD thickness is limited by the design of the backlight. The move towards LED backlighting is making LCD televisions slimmer.
Both technologies take a back seat to AMOLED screens which for all intents and purposes are not limited in thickness at all.
Plasma screens are heavier than LCD screens. This is because plasma relies on a vacuum and the glass must be thick enough to withstand the associated forces ( 15 pounds per square inch of atmospheric pressure ).
 Viewing Angle
All plasmas support wide viewing angles. The best LCDs will approach plasma viewing angles. The worst LCDs have abysmal viewing angles.
 Response Time
Plasma response time is virtually instantaneous because plasma is fundamentally electronic. LCD response time is a serious issue and is not instantaneous because LCD switching is mechanical in nature - liquid crystal must physically bend for the color to change and this can never be instantaneous.
Response Time of LCDs has been recently improved to the point where in combination with strobing backlight the quality of moving video has ceased to be an issue.
The advent of 3D television however has resurrected the switching time issue because the principal 3D technology relies on constantly switching between "left" and "right" frames. In a normal video successive frames are identical unless the object is moving. in a 3D video successive frames displayed may all be different without any motion being displayed simply due to the left-right alteration. LCD screens available so far are not fast enough to switch flawlessly at the rate required for 3D television.
 Phosphor Burn-In
Only plasma ( and CRT ) uses phosphors so only plasma suffers from phosphor burn in.
 Design Life
Many plasma manufacturers boast a life span of 60,000 hours to half life! This is a longer life than a tube based television. The specification is somewhat suspect since the process of determining longevity of the product is based on deductive mathematical calculation of phosphor dissipation, and does not take into account the electronic components and the myriad of problems that can occur.— Plasma TV Buying Guide , How Long Do Plasma TVs Last?
LCD television manufacturers claim that their displays last, on average, 50,000 to 65,000 hours. In fact, an LCD TV will last as long as its backlight does - and those bulbs can sometimes be replaced! Since this is nothing more than light passing through a prismatic substrate, there is essentially nothing to wear out in an LCD monitor. However, one nasty little known fact about LCD technology is that as the backlight ages it can change colors slightly (think of florescent office lighting). When this occurs the white balance of the entire LCD TV will be thrown for a loop and the user will need to re-calibrate, or worse, try to replace the backlighting or ditch the unit altogether.— LCD TV Buying Guide
Plasma screens use glass and thus are more fragile than their LCD counterparts and should be installed by professionals, especially if the screen will be mounted on a wall. LCD screens use plastic.
LCD Brightness is limited only back light, which in turn is only limited by power available from the outlet. LCD flat panel TVs can be made as bright as is necessary. Transflective LCD panels can even be viewed in direct sunlight.
Plasma Brightness is fundamentally limited both by the phosphors and by Plasma's low efficiency requiring high power consumption to display large patches of brightly lit screen surface. Plasma panels aren't well suited at all for bright rooms. Plasma is also subject to a half life. That is to say that every couple of years the brightness will be halved, even if the unit is not in use. This continues until the unit is discarded.
 Display Technology
LCD displays consist of a layer of liquid crystal, sandwiched between two polarizing plates. The polarizers are aligned perpendicular to each other, so that light incident on the first polarizer will be completely blocked by the second one. The liquid crystal is a conducting matrix with cyanobiphenyls (long rod-like molecules) that are polar and will align themselves with an electric current. The neat feature of these molecules is that they will shift incoming light out of phase when at rest. Light exiting the first polarizer passes through the liquid crystal matrix and is rotated out of phase by 90 degrees, then it passes through the second polarizer. Thus, unpowered LCD pixels appear bright. When an electric current is passed through the crystal matrix, the cyanobiphenyls align themselves parallel to the direction of light, and thus don't shift the light out of phase, the light is blocked by the second polarizer and the LCD appears black...
PDP's have been under development for many years, and provide rugged display technology. A layer of gas is sandwiched between two glass plates. Row electrodes run across one plate, while column electrodes run up and down the other. By activating a given row and column, the gas at the intersection is ionized, giving off light. The type of gas determines the colour of the display. Because it has excellent brightness and contrast and can easily be scaled to larger sizes, PDP's are an attractive technology. However, their high cost and lack of grayscale or colour have limited applications of PDP's. However, advancements in colouring technology have allowed some manufacturers to produce large full-colour PDP's. In future, large colour PDP's will be more common in workstation and HDTV applications.— Monitorworld.com , What types of flat-panel displays are available?