Easier to use and low costs
Vanguard leads in innovations that truly add value for investors. Vanguard offers the largest choices of index funds to facilitate diversification. I trust Vanguard like I have never trusted a fiduciary. Most of all I value the decency and sincere helpfulness of many of the personnel at Vanguard I have had the privilege of dealing with. Stephen Hoenack, a very appreciative customer.
Lower charges. Only company which is on its investors side.
Fidelity managers change often; now they work in teams. They also do not invest in their own funds! Morningstar rates management a C.