I disagree. Firstly, there is no such thing as an LED TV. I believe you've seen higher end LCD reviews where peak black levels are measured, which are indeed impressive. Means nothing in real life though as it's a fraction of the screen being measured. Self-lit pixels will, logically, always have the best constant black levels throughout the panel.
Where people get muddled is they see a high end LCD with 0.02cd/m, and then other high end plasmas with 0.02 / 0.03cd/m. They think that the LCD is then as good / better than the plasma, without having the basic understanding of flat panel TVs, and more so just exactly what the testing of TVs involves.
To them, the cd/m rating is one that applies to the entire panel in any scenario of varying darkness/brightness/colours. Wrong.
An LCD displaying a white bit(s) will still be letting light through to display blacks. This is the disadvantage of LCD which uses a backlight(s) for all/most pixels.
Black level is the most important factor in determining contrast ratio. The higher the static contrast ratio, the better the picture quality. Contrast ratio being the difference between the darkest black and brightest white. Brightness is a non-issue as there are virtually no modern/decent TVs that struggle with it.
Even then, contrast ratio can't paint the entire in real life experience. Self-illuminated pixels always win in real life.
Besides having a better contrast ratio, plasma also destroys LCD when it comes to lower input lag and better motion handling. Plasma pixels have sub 0.5ms response times.
Image retention is a non issue, and has nothing to do with picture quality. It is barely noticeable, and is gone within seconds.
If you want to use your TV without having to be somewhat conscious about IR and image burn in (which again is a non issue nowadays due to its prevalence and ability to easily avoid), and sacrifice that for overall picture quality and experience, then that is your prerogative.
