In the DC plan the retire assumes the risk and there is no guarantee of a return sufficient to retire on. Also as one gets older one should invest in safer assets like GICs. They pay nothing. 
In a DB plan the risk is assumed by the government (or company) and is preferable to the DC plan.  If there is a shortfall the government makes it up. The rates of return on theses government pension pans are based on what happened years ago when rates were much higher. 
Further more you do not mention the massive transfer of wealth from the private sector to public service pensions plans who hold about a TRILLION dollars in assets which will flow to civil servants in the next few years.