The key issue in operations is being able to come home safely and go the next day, and because of the very low observable stealth and the other capabilities that are incorporated in fifth- generation aircraft, the risks to the operator are diminished significantly and the chance of coming home is far increased, which enhances survivability. The difference in that kind of technology between fourth and fifth generation is of such a magnitude that there is no comparison.
On September 15th, 2010. See this statement in context.