The new consumer reports just came out with reviews of LCD and Plasma TV's. They recommended getting a 1080p TV for 50" and above, but below 50" they said that 780p is just as good due to the screen size. In fact, they rated a few 780p TV's with better and clearer pictures than some 1080p sets. However they stated that when watching good blu-ray movies you might be able to see some subtle differences.

Go with 1080p!