This is the response I gave to one of my wife's friends. It is a collection of a bunch of responses I got from here.
Almost every single solid review you read will state, flat out, that LED is
great, but a good plasma will provide about the best image you can possibly
achieve. They like the Elite Sharp LCDs, but beyond that, most of them are
'really good' at best.
Plasma still has inherent qualities that LCD (whether LED or traditionally lit)
can't match. Mostly this is because of the emissive technology and the real
world refresh rates, which create smoother motion, better off-axis viewing, and
better black levels.
LCD gets brighter and doesn't have much in the way of image retention issues,
but if you've lived with a plasma for a while, then that isn't an issue for you.
The ST/GT series from Panasonic offers one of the best images you will obtain
for the money right now. A nice balance of image quality to price. The 7000/8000
series from Samsung is also a good place to be looking.
I would simply not be buying an LED if I was after the best image quality. LCD
is great for secondary display locations, but not something I would recommend in
the primary location to most people.
If the room is dark or you have good control, then there is no reason at all you
shouldn't use a plasma.
LCD has issues. Higher refresh rates help deal with some of them, but they still
have some small issues. Image uniformity, black levels, angle of viewing issues,
blurring.
The soap opera effect can be turned off on ALL LCD TVs so I don't consider that
something to worry about. If you like it, use it, if you hate it, turn it off.
The soap opera effect is the use of creative frame interpolation (CFI) or Motion
Flow or a dozen different names by manufacturers. CFI converts a 60hz source
(ALL TELEVSION!) and deblurs the image and inserts new frames between them. A
120hz display can convert a 60hz image (60 frames) into 120hz (120 frames). A
240hz display may be capable of delivering 240 frames
But, at the end of the day, if you've done your homework then you should be
aware that plasma produces a more natural image from all viewing angles with
better black levels and a smoother image. This is just a natural aspect of the
technology being used. The active light engine of plasma really delivers a
better image.
But, LCD is more 'versatile' when it comes to brighter rooms and rooms with lots
of windows.
But, any room that you want the best possible image in really asks to have a
plasma in it. Just for reference, I have 3 plasma's even one in my bright living
room. It works great but it has a louver filter that controls overhead lighting.