With an IRA, "there are a lot more investment options," says Bendix. "With a 401(k), you're limited to your employer's selections. And they may not be in tune with what your objectives are."
But some experts give the 401(k) extra points for its flexibility.
One option you'll often see in a 401(k) that is not offered in IRAs: stable-value funds. And since they traditionally offer a higher return than money market funds, they can be a great place to park cash for your upcoming retirement, says Wayne Bogosian, president of The PFE Group and co-author of "The Complete Idiot's Guide to 401(k) Plans."
The average annual return: 2.65 percent, according to recent numbers from the Stable Value Investment Association, an industry group based in Washington, D.C.