VTGLX has slightly higher fees but it may save a few nickels in taxes, especially for someone who makes Yellen's income.
The Vanguard 500 index fund (VFINX), which is inherently very tax efficient, has $143 billion in assets. Yellen's VTGLX has only $3 billion. VFINX has a 5 year average return of 9.90% vs 9.96% for the VTGLX.