Go and look at the two back to back in Curry's or similar shop - That's the only way you can really see the difference in picture quality.
The difference between LCD and Plasma is pretty big, and I personally prefer LCD's - They seem brighter and due to not having a glass screen you don't get reflection or anything if you have the curtains open and TV on during the day.
I've had my Sony LCD for about 2 years now and it's been superb, looks great even at a 70 degree angle.
Guess it all comes down to personal preference (and budget of course) but i'd suggest going to look at the two around your budget and see what YOU prefer as everyone has an opinion but it's not always right
