Updated November 2013!
In television technology trifecta of LED LCD, plasma, and LCD, which comes out on top? The subject of countless debates and diatribes, the better question is: which works best? Or more precisely, which works best for you?
When you cut through the hype and the fanboys, each tech has different benefits and costs. So to help you figure out which TV is right for your house, let's take a look at each one.
First, a BIG disclaimer: any article of this type is, by necessity, going to contain a lot of generalizations. In most of the categories below, there are likely one or two exceptions to each rule. It's great to find an outlier, but that's just what it is, an outlier. The "average" product featuring these technologies is going to perform as listed.
Second, some terminology.
Plasma TVs, made by Panasonic, Samsung, and LG, range in size from 42 inches to roughly 65 inches. There are some larger models (notably Panasonic's 150-inch), but for most people, they max out at 65 inches. Most are "600 Hz" which isn't quite the same as 120 Hz or 240 Hz LCDs (more on them in a moment). You can read more about it in What is 600 Hz?
LCD TVs range in size from a couple of inches, to 90 inches, and everywhere in-between. They're made by everybody. All "LED TVs" are actually LCD TVs, they just use LEDs as their light source, instead of the traditional CCFLs. There are very few CCFL (non-LED) LCDs on the market anymore. Since you might find a few off-brands that still use CCFLs (or you own a CCFL LCD and want to compare), we'll include them here separately. One of the most common features of higher-end LCDs is 120 and 240 Hz refresh rates which helps reduce the blurring of motion common with LCDs. You can read more about that problem and the solution in What is Refresh Rate?
You might ask yourself, at this point, why only three companies for plasma? When electronics companies started building their manufacturing plants for TVs, they faced a choice: make big "cheap" flat panels that can't go much below 42-inches (plasma), or build a more expensive factory that can make a wide variety of sizes, even though the bigger sizes will be more expensive (LCD). As production has increased, the larger LCD sizes have become more price competitive, so that distinction has disappeared. As such, you don't see a lot of companies investing in new plasma TV manufacturing. Not when an LCD factory can make everything from cell phone screens to 90-inch HDTVs (an over simplification, but you get the point).
If you're not sure what size TV you should be getting, check out How big a TV should I buy?
If you're interested in how LCD and plasma match up against OLED, check out LED LCD vs. OLED vs. plasma.
Light output (brightness)
Winner: LED LCD
Runner-Up: CCFL LCD
Without question, LED LCDs are the brightest TVs you can buy. Some models are capable of well over 100 footlamberts. To put that in perspective, in a movie theater you're lucky if you get 5. CCFL LCDs are a close second.
Plasmas just aren't that bright. It's all relative, though, as plasmas are still likely way brighter than old-school CRT tube TVs. So plasmas aren't "dim," but they aren't nearly as bright as LCDs.
The question is, do you need that light output? In a dark room, 100 footlamberts will be searingly bright, and could cause eye fatigue. In a bright room (daytime/sunlight) a plasma might be hard to see.
Another aspect to consider is any antireflective or antiglare material on each screen. A plasma with a really good antireflective coating may be better to watch with room lighting than a glossy-screen LCD with no such coating (and vice versa).
Check out LED LCD backlights explained for more info on why LCDs are so bright.
Loser: CCFL LCD
Runner-up: LED LCD
This is getting a lot closer, but plasmas still offer the best black levels. Yes, LED LCDs can sometimes have an absolute black (by turning off their LEDs), but when you're watching a movie, plasmas are going to seem darker. This relates to contrast ratio...
Loser: CCFL LCD
Runner-up: LED LCD
Contrast ratio, or the ratio between the darkest part of the image and the brightest, is one of the most important factors in overall picture quality. A display with a high contrast ratio is going to seem more realistic, and have more virtual "depth." I highly recommend reading this article: Contrast ratio (or how every TV manufacturer lies to you).
There are a few exceptions. The Samsung UN-85S9, for example, has an advanced local dimming backlight, which gives it a plasma-like contrast ratio... for a price. A big price. A $40,000 price (that's not a typo). A few other LCD have very good local dimming, but most still don't have the visual punch of the best plasmas. One good LED LCD doesn't make them all good, nor does it herald a new generation of better LED LCDs. The Samsung doesn't do anything new. It's a local dimming LED LCD. We've actually seen fewer and fewer of this types of displays for the reason the Samsung makes quite obvious: price (though there are cheaper full array local dimming LCDs, they're just rare). Local dimming LED LCDs are more expensive than edge-lit models (and much more expensive than plasmas, at the same size), and these days, expensive TVs aren't big sellers.
Do a few other local dimming models come close to the better plasmas (or exceed the lesser ones)? Yes, but again these are the exceptions, not the rule. Check out LED LCD backlights explained for more info.
There are some technologies coming down the pike that may offer even better contrast ratios. One of the most exciting is OLED. I'm really excited about OLED. It promises to be the best of all words: the best picture quality going, ultra-efficient, and incredibly thin. The first two models, anLG and a Samsung, are impressive. To learn more about this upcoming TV technology, check out What is OLED TV? and OLED: What we know.
So, on average, plasmas have a better contrast ratio (with notable exception noted). If you're curious why they don't look like it when you see them in a store, check out Why do plasma TVs look washed out in the store?
Winner: LED LCD
Right now the only Ultra HD "4K" TVs on the market are LED LCDs. It's unlikely we'll see 4K plasma, now that Panasonic is pulling out of the plasma business. Keep in mind that resolution is only one aspect of a TV's performance. I did a recent comparison of a 50-inch 720p TV and a 50-inch 4K TV and found the 720 looked better (and in some cases, more detailed).
Loser: LED LCD and LCD
Motion blur is when an object in motion on-screen (or when the entire image pans/moves) blurs. Some of this is in the camera when the scene was recorded, but most is done by the TV. Not everyone notices it, not everyone is bothered by it, but it's there, predominantly with LED and regular LCDs. The 120 Hz and 240 Hz higher refresh rates were developed to minimize motion blur. To some degree this works, but often the processing to create this cause an ultra-smooth image, which is called the "Soap Opera Effect." SOE, REALLY bothers some people (myself included). Some people like it.
Winner: Plasma, LED LCD, LCD
It's important to understand that the only reason LCDs have higher refresh rates is to combat motion blur. Since plasmas don't have an issue with motion blur (not nearly to the same extent, anyway), they don't need higher refresh rates. In reality, the way LCDs and plasmas create images are so different that you can't compare th refresh rate of one with the other. Check out What is 600 Hz? (plasma) andWhat is refresh rate? (LCD) for more info.
Loser: CCFL LCD/LED LCD
Runner-up: IPS LCD (see text)
How big is your room? Do you or loved ones sit off to the side, viewing the TV at an angle? If so, it's important to note that LCDs of both flavors lose picture quality when viewed "off axis," as in not directly in front of the screen.
Small room, small couch, mother-in-law Barcalounger off to the side? Don't worry about it.
Somewhere in the middle are in-plane switching LCDs, which offer a better viewing angle at the expense of overall contrast ratio and black level. Check out my article Myths, Marketing, and Misdirection for more info.
Winner: LED LCD
Runner-up: CCFL LCD
No question, LED LCDs have the lowest energy consumption, especially when you turn down the backlight. Prius drivers, this is the TV for you. CCFL LCDs are a close second, with the same addendum.
Plasmas, especially when you turn up the contrast control (which you need to for them to look their best), just aren't as energy efficient. They are, however, far better than they were a few years ago.
If you want to go green, get an LED LCD. As I mentioned in the Myths article, though, it won't save you money. Because LED LCDs are more expensive than other TVs, it will take you years to make up that difference in energy savings (if ever). We're talking a few dollars difference in a year here. Check out What you need to know about power consumption.
Winner: CCFL LCD
Loser: LED LCD
Because they tend to be at the lower-end of a company's TV offerings, or off-brands, CCFL LCDs are the cheapest TVs you can buy.
The cheapest "doorbuster" TVs will almost always be CCFL TVs. Plasmas tend to have the best size/price ratio. In some cases, plasmas can cost half as much on a per-screen-inch basis than big LED LCDs.
Multiple studies by a variety of sources have found flat panel TVs to be extremely reliable. Internet forums are always populated by the angry, so invariably you're going to read more "well mine broke!" posts than "I've had mine for 5 years and it's great." Check out How long do TVs last? for more info.
Gotcha! All TVs can burn in. It's unlikely you'll abuse them enough for this to happen (think airport arrival/departure displays). Both LCDs and Plasmas can have image persistence, which has the outward appearance of burn-in, but isn't permanent. Plasmas are more likely to exhibit it. For more on this, check out my article Is plasma burn-in a problem?
The short version? You're going to notice image persistence long before it will become a problem.
Loser: CCFL LCD/LED LCD
Uniformity, or a consistent brightness to the image, doesn't bother me a lot. It bugs David a bunch, though. Check out my article Is LCD and LED LCD HDTV uniformity a problem?
Plasma can have issues in this regard as well, though they're far less frequent or noticeable. Edge-lit LED LCDs are the worst offenders, though cheap CCFL LCDs and backlit LED LCDs have their own issues. In many cases, the uniformity can vary per sample. So your TV might be fine, but your brother-in-law hates the one he bought of the same model. I linked to it before, but LED LCD backlights explained it's worth checking out for more on this too.
And the winner is...
If you want to count wins and losses from the list above, have at it. The thing is, these items don't have equal weight. That's the point. For one person, absolute light output is absolute, for another, black level is above all else. These two performance aspects are, for now, mutually exclusive.
So don't listen to those who say, "well, its brightest, it's best" or "LCD's black level is terrible, so they blow." Brighter is not necessarily better, and black level isn't everything. Reading through this list I'm positive you've mentally weighted certain factors above others, even if you didn't notice it at first. Go with your gut. If you watch a lot of TV during the day, or have a room with lots of windows, LED LCD is probably best. If you watch at night, and want the TV to disappear into the background, plasma is probably best.
Want to know the best part? The dirty little secret of the TV world? If you're buying a name-brand TV, its picture quality is going to be really, really good. You are seriously picking from good, gooder, and goodly goodest here. Compared with flat panel TVs from just a few years ago, new HDTVs are thinner, brighter, bigger, better-performing, and cheaper than ever before. So have at it. Your new TV is going to be awesome for years to come.
Got a question for Geoff? First, check out all the other articles he's written on topics like HDMI cables, Active vs Passive 3D, and more. Still have a question? Send him an e-mail! He won't tell you which TV to buy, but he might use your letter in a future article. You can also send him a message on Twitter @TechWriterGeoff or Google+.