In the five years to September 2026, VOO returned 13.8% a year and VTI returned 12.6%, dividends reinvested. VTI holds essentially the same large companies as VOO, plus thousands of smaller ones. Because both weight by size, those smaller companies are a small slice of VTI, and the two funds move together almost all the time.
For a representative saver about twenty years from retirement, investing in a taxable account: On known costs alone, VOO and VTI come out about even here. VOO's 2.6-point lead in the plan's success rate comes from how the two funds performed over the last five years, so it holds only if those years repeat.
With only the known costs — the same market for both funds, differing by fees and dividend tax — the money lasted in 97.4% of 10,000 simulated futures with VOO and 97.5% with VTI. Using each fund's own returns from October 2021 to September 2026 instead, the figures were 98.5% and 95.9%. Both funds were run against the identical sequence of market shocks.
What VTI adds. Mid- and small-cap companies. They are thousands of names but a small share of the money, so they nudge VTI rather than redefine it. In years when small companies beat large ones VTI edges ahead, and the reverse in years they lag.
What does not differ. Fees, dividend yield and the tax on it are close to identical, which is why the known-cost result above is flat. Any gap you see in the second scenario comes from which of them had the better last five years.
VOO tracks the S&P 500 — it holds the 500 large US companies in the index, weighted by size. VTI tracks the Morningstar US Total Market Index — it holds large, mid and small US companies across the market, weighted by size.
VOO charges 0.03% a year and yields 1.04%; VTI charges 0.03% and yields 1.03%.
Returns and volatility are measured from monthly returns with dividends reinvested over 60 months — one sample from one market, and weak evidence for telling two broad funds apart, which is why the known-cost result is reported first. Dividends are taxed at 15% in a taxable account by default, the qualified rate most households pay; the page also shows the 0% and 20% brackets. It is the only tax modeled. A 3.8% net investment income tax can also apply to dividends once modified adjusted gross income passes $200,000 ($250,000 joint); it is not included. Retirement spending is held at 70% of income in today's dollars, and contributions exclude any employer match.
Neither, in any way you can know in advance. Their fees and yields are nearly the same, so the only difference is whether large US companies beat smaller ones from here, which nobody can forecast.
There is little point. The large companies that make up VOO also make up most of VTI, so holding both mostly means owning the same companies twice.