I have a Panasonic Viera, my in-laws have a Sony and my mum has a Samsung. All LCD.
The Sony is flat and lifeless (I did play with the settings and got it much better, but my father-in-law didn’t like it and put it back to factory settings). The Samsung plays standard broadcast quite well but is very ‘soft’ – which is, I assume, their attempt to hide pixelation. The Panasonic generally shows pictures very well – certainly on DVDs, BluRay and gaming. It does fall over a bit sometimes with some daytime broadcasts/broadcasts from older originals.
You simply have to go into a shop and compare, like-for-like, different sets showing the sort of programming you watch most of.