Plasma uses more power
Plasma is heavier
Plasma has ghosting
Plasma's aren't improving much compared to LCD
Plasma's are more expensive (comparing the models people commonly buy, not the high end stuff)
There aren't as many plasma TV's as LCD
That's why they're dying. In terms of quality both are so poorly setup out of the box it doesn't really matter which is better. As for screen viewing angles and glare it depends more on the face of the display, there are models in both classes that suck and are great, thankfully we're going back to matte screens.
You have to remember, the electronics that survive are the ones that go mainstream and don't aim for the high end markets. That's why Betamax died (CD/MP3 and Netflix/BluRay are a different type of battle). Plasma's made the early mistake of trying to be too good instead of good enough, it cost them.