"string" :string
one has two quote marks; the other only one colon.
But "less keystrokes" is a glib argument in favour of symbols... a better reason for using symbols over strings is that symbols are more efficient in memory. They act like pointers to a single string, where quoted-strings all exist individually in memory, so if you use the same string a lot, you use lots more memory than if you use the same symbol a lot.