Plasma still has the best motion response and the most realistic colors. LED LCD's are getting close and are physically smaller and lighter. If you can deal with a couple of inches of thickness and a few more lbs, plasma is the way to go right now imho (also less expensive than an LED LCD). I've yet to see any serious source rank an LED LCD much less a LCD above a plasma for picture quality.
Re resolution and refresh rate, the above poster is mistaken, they are all the same resolution (by definition a full HD TV is 1920x1080 - stay away from the 720p wanna-be TVs unless you are getting something <40" and aren't super picky). Plasmas have a dramatically higher refresh rate, though at some point the marginal value of refresh rate diminishes. A mid-range panasonic plasma is 600hz, to my knowledge you can't buy any lcd with a rate that's nearly as fast. But this doesn't matter a lot.
Where plasmas still pwn the rest are contrast ratio - nothing else can generate the blacks that you'll get from a plasma. A mid range plasma is 2 million :1.
Plasmas can't compete on form factor, thickness or weight, so if these matter an LCD or better yet LED LCD can be much, much better.
You could get a panasonic TC-P502 (50" full HD plasma) for under $700 if you shop around -this seems to be about the most value for money for a tv currently (
http://www2.panasonic.com/consumer-electronics/shop/Televisions/All-VIERA-Flat-Panel-HDTVs/model.TC-P50S2.S_11002_7000000000000005702#tabsection). The 42" version of the same should be under $600. Check if your employer has a panasonic EPP program.
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