Keep in mind there is a lot of FUD out there about plasma...most of it is exaggerated or simply not true. If anyone claims any one technology is obviously better then compare them with a person that says that one DSLR brand dominates all others. Each technology has its pros and cons. Each technology's list of cons has shrunk since both were introduced.
To give you a run down.
LCD:
Pros-
Very bright(only important in very bright rooms...but impressive none-the-less on the shelves at stores)
Smaller screen sizes availabe
Lighter(weight)
Better for use as a external computer monitor
Cons-
Some motion blur still evident in some models(especially budget models)
Less color accuracy
Less contrast(Ignore dynamic contrast ratios...they're lies)
More Expensive
Plasmas:
Pros-
Very high contrast ratio
Accurate colors
No motion blur
Better for movie watching(movies tend to need high contrast because they have many dark scenes)
Cons-
MAY use higher power
MAY run hotter
Heavier
Only available in larger screens
Now I would like to discuss the issue of power. Power ratings are actually closer than many people would have you think. Even someone in this thread claimed plasmas suck power. This is an exaggeration. In general, they do tend to use a bit more power. However, you have to pay attention to how manufacturer's rate power. LCD's are ALWAYS drawing max power. The lamp is always on and that is what draws most of the power.
Plasmas have a variable power rating. This is because it depends on what the screen is showing. If the screen is dark, it will be pulling minimal power. If its showing a white screen it will pull max power. So the true power rating isn't always what its listed as. That is often the MAX power rating. As we know from photography, scenes are often 18% grey, movies are generally even darker. So I really wouldn't listen to people who claim that one technology obviously has the power advantage.
In similar respects, as plasmas have improved their efficiency, LCDs have improved their contrast ratio. They still don't match those of Plasmas, but they aren't the "dark grey" that was so common years ago. This also applies to image rentention. Do not be fooled, image retention happens on LCDs and Plasmas and CRTs. Plasmas WERE more susceptible to them a decade ago, now, its a virtual wash. You can find reports of LCD users having the issue and you can find plasma owners having the issue.
So...at the heart of the matter...I usually boil it down to a few key questions:
Is the room you are putting the TV in get direct sunlight(on the TV itself) during times when you want to watch TV?
(If yes, +1 point for LCD...if not....draw)
Is the room you are putting the TV in typically fairly dimly lit and/or dark?
(If yes, +1 point for plasma...if not...draw)
Is the room a larger room that would benefit from a larger TV?
(If yes, +1 point for plasma)
Will the TV be used as a computer monitor?
(If yes, +1 point for LCD)
Will the TV be used in a home theater/for movies?
(If yes, +1 point for plasma)
I could ask other questions but I think that sums up the major considerations I would make. If going plasma, Panasonic is pretty much the go-to brand. LCD is Samsung, Sony and occasionally a standout from a different manufacturer.