For a while, big LCDs simply weren't as good as plasmas. They took more time to generate an image (milliseconds, but it makes a difference), which meant that scenes with a lot of fast-moving action could become distorted.

Now the better Japanese- and Korean-made LCDs are much speedier and have relegated that problem to bargain-basement models that may still have difficulty keeping up with, say, Luke's X-Wing as it heads toward that vulnerable spot on the Death Star.