Gmail adds a very simple feature: a contact picker. When you compose a message, you will see the list of contacts so you can select some of them.
But all people use Auto-complete because it is convenient and fast, and usually does the trick. But sometimes seeing your list of contacts can help you remember all the people you want to include on your email.
The contact chooser also works for groups.
The feature also works for “cc” and “bcc
