In very general terms, you'd expect the 120Hz display to be better in every area, due to the superior electronics. You'd expect, for example, it to correctly de-interlace and upscale lower res images with better quality. Experience teaches us though that expectations and reality do not always meet. The only way to evaluate such things is through online reviews, since in-store staff don't have a clue. If the price difference is small, by all means go with the 120Hz model. It will play with HD disc players better and should do a better job of displaying HDTV images too. Though it's also good to note that at screen sizes smaller than 50", the differences are not always easy to see.