Hi,
HD-ready displays images up to 1080i. The "i" meaning interlaced (horizontal lines are displayed one after the other). Full HD displays images up to 1080p. "p" means progressive, where the lines are displaced simultaneously.
So, for less action-packed movie sequences, HD-ready will suffice. However, watching motion-intensive scenes like car chases and the like, a full HD display will output the images much more faithfully.
Hope this helps...