Simple answer.... less than $2000 Plasma is going to be a better bet. Higher contrast, truer colors, great viewing angles. Panasonic models in the $600-1800 are awesome. 42" - 50"
Greater than $2000 it is a wash and depends on features, sales, options, etc.
I have had plasma for three years and never found a better bang for the buck in the less than $2000 price range. A fellow enthusiast at work fully agrees with me.
If you want to do the foot work and verify what I am claiming.....avsforum.com
Best bang for the buck if you are not viewing within 5 feet is a 50" 720p Panasonic Plasma going for ~600-800. 1080p makes little (if any viewing difference) if viewing past 5' on anything smaller than a ~60" (Additionally, there isn't much true 1080p content today)