Theoretically there's a better expected value with the 401K, but that's not what almost anyone wants. People want a moderate upward trend in value with no chance of going under.

An interesting place to see this is in groups of US military members talking about the pension plan they just had the option to switch. The 401k version has a higher expected value than the pension version, yet many people who are themselves sticking things out to pension age prefer the pension age. Though it may be that people staying in the military trend risk averse.