The start of a New Hope tells us everything we need to know about the Empire and the Rebellion all in one huge, and grandeur shot that once again, is a mix between practical and special effects.
The opening crawl and first scene from A New Hope is both more tragic (you feel for those who lost their lives to get the plans, because you now know them) and even more urgent (you immediately understand its importance, because you've seen what the Rebels sacrificed).