A hypothetical joke, but I really feel there isn't a big difference in safety of your funds.
It's really funny when you think about it. The government spent themselves into huge debt and failed to budget and invest properly, but they tax you and your employer on the premise that you can't be trusted to budget and invest properly for later years and need a safety net.
What are your chances of getting a payout from a C- or lower book, 50/50? What are the chances someone under 45 gets all the social security coming to them?