There's also the fact that newbie characters will eventually have that "moment of truth" where they realize the potential of their powers, make full use of them, and kick everyone's ass.
Dblade is right, the White Lanterns arise exclusively in response to the Blackest Night, and they aren't even an established Corp like the Red or Green Lanterns. They're connected to the entity of life just like the Black Lanterns are connected to the entity of death. Also, don't the WLs only arise when all 7 corps have united or something?