There is not any difference in the Sitefinity code base when you go from one edition to another. Actually, it is the license key which turns features on and off for you. So from the perspective of the Project Manager all things are equal.
As for the features included, you can go to the page here
and compare them.
@William The main idea with the Intranet edition is to allow customers to have a more flexible and adequate for them pricing model when it comes to having an intranet project with lots of simulatiously logged in back-end users.
Do you want to have your say in the Sitefinity development roadmap? Do you want to know when a feature you requested is added or when a bug fixed? Explore the Telerik Public Issue Tracking
system and vote to affect the priority of the items