What is the difference between the two 'Story Mission' Icons?
On Destiny, there appears to be two different icons for story missions:
one slightly smaller with just a star (e.g. Earth - The Dark Within).
one larger with a star within 'wings' (e.g. Earth - Restoration)
What do these different icons represent?
See the image below:
The star with wings is a main story mission, often playing a huge part in the story with a cutscene or other grand event.
The single star mission is more of a sidemission. There is no requirement to complete them, but they do offer more story and, of course, rewards.