(MONEY Magazine) – In an attempt to one-up each other in the hotly competitive 401(k) market, Fidelity and Vanguard are each planning to roll out new Web-based personalized-advice services this spring. "It's definitely the trend of the future," says Vanguard's head of institutional sales and marketing, Shellie Unger. While investors in many 401(k) plans can already access educational and account information via their PCs, this new wave of online services would generate investment advice based on personalized details such as your age, salary, number of kids and years until retirement.

Fidelity's PortfolioPlanner, which is scheduled to go live this spring, will ask about your goals, risk tolerance and annual savings, then create a multicolored pie chart proposing an ideal asset allocation for your 401(k), using the specific funds available in your plan, says Robert Reynolds, president of Fidelity's institutional retirement group. Vanguard's Participant Online will also help you select funds and will tailor the news and educational links on your screen to your needs.

The cost of these new interactive services will be wrapped into administrative fees charged to employers--fees that are often passed on to plan participants. "A lot of these bells and whistles are there to justify excessive costs," gripes pension consultant Steve Butler of Lafayette, Calif. But as long as you're paying, he adds, "Make sure you use it."

--Lisa Reilly Cullen