It really depends on what you intend to use the screen for and how much you are into home cinema.
The Sony screen is a mighty fine screen, although the S series lags behind the company V series for outright image and sound quality.
I'm not familiar with the Toshiba you have shown, however there are alarm bells ringing. Either it is an absolute steal at the same price as the Sony or it has been compromised in performance - I suspect the latter.
I have recently bought a Panasonic TH37PX60 plasma, which should be only a little less in price but has been described by users and the press as absolutely awesome - an it is.
LCD screens are better for static images and games - so if you are going to be using an Xbox 360 or PS3 then LCD will be a more sensible option.
Plasmas tend to be better on overall contrast and motion, and can suffer from screen burn (although modern displays are much better than older ones) and as a result are better for DVDs and normal TV.
Do remember this is a rule of thumb and not cast iron in any way.