This is analysis, not personalized investment advice. Do your own homework before making decisions.
If you are buying and holding for decades, VOO is the best default choice. It tracks the S&P 500 at 0.03% expense ratio — cheap, simple, and proven. If you actively trade options, SPY's unmatched liquidity makes it worth the higher fee. And VTI adds small-cap stocks to your exposure, but those extra ~2,000 holdings contribute very little to long-term returns compared with the 500 large-caps you already get from VOO or SPY.
What each fund actually is
VOO — Vanguard S&P 500 ETF
VOO tracks the S&P 500 Index: 500+ of the largest U.S. publicly traded companies across technology, healthcare, financials, consumer staples, industrials, and more. It is market-cap weighted, meaning Apple, Microsoft, NVIDIA, Amazon, Alphabet, Meta, and Berkshire Hathaway carry the most weight. Expense ratio: 0.03%. AUM: ~$918B. Inception: 2010. VOO is Vanguard's answer to SPY — same index, same low cost, different sponsor ecosystem.
VTI — Vanguard Total Stock Market ETF
VTI tracks the CRSP U.S. Total Market Index, which includes large-cap, mid-cap, small-cap, and micro-cap stocks — roughly 3,520 holdings across the entire investable U.S. equity market. About 80% of its weight is in large-cap stocks (the same companies you'd find in VOO or SPY). The remaining ~20% covers mid-caps (~14%), small-caps (~4%), and micro-caps (~2%). Expense ratio: 0.03%. AUM: ~$620B. Inception: 2001. VTI is the simplest way to own every U.S. stock in one ticker.
SPY — SPDR S&P 500 ETF Trust
SPY tracks the same S&P 500 Index as VOO. Same benchmark, roughly the same ~505 holdings in similar weights. The key differences: SPY is a unit investment trust (UIT) rather than an open-end ETF, which makes its structure more rigid for dividend reinvestment. More importantly, SPY charges 0.09% — three times VOO's fee — but compensates with unmatched trading volume (~72M avg daily shares) and the deepest options market in the world. AUM: ~$725B. Inception: 1993. SPY is the original ETF, launched before most of its competitors existed.
Side-by-side comparison
| Feature | VOO | VTI | SPY |
|---|---|---|---|
| Index tracked | S&P 500 | CRSP U.S. Total Market | S&P 500 |
| Expense ratio | 0.03% | 0.03% | 0.09% |
| AUM (approx.) | ~$918B | ~$620B | ~$725B |
| Holdings | ~503 | ~3,520 | ~505 |
| Avg daily volume | ~7M | ~5M | ~72M |
| Structure | Open-end ETF | Open-end ETF | UIT |
| Best for | Buy-and-hold | Total market purists | Options traders |
Data is approximate and time-sensitive. AUM, holdings count, and volume figures shift daily. Expense ratios are fixed as of publication. Source: Vanguard, State Street, and fund prospectuses.
The cost analysis — what 0.09% vs 0.03% actually costs
On the surface, 0.06 percentage points doesn't sound like much. But over decades and real dollar amounts, it adds up to something meaningful. Here is the math with concrete numbers.
$50,000 invested · 30 years · 7% annual return
That $9,364 is the cost of paying three times the fee for essentially identical S&P 500 exposure. It is not a trivial amount — it could buy a used car, fund several years of brokerage fees, or compound into significantly more over time if reinvested.
For smaller amounts the gap narrows but doesn't disappear: on $10,000 over 30 years at 7%, SPY costs about $2,809 in fees versus $562 for VOO — a difference of roughly $2,247. The percentage is always the same (three times the fee), but the dollar impact scales with your investment size.
The real question: VOO vs VTI — does the small-cap addition matter?
This is the comparison that trips up the most investors. VTI has 3,500+ holdings while VOO has ~500. That sounds like a massive difference. But here's what most people don't realize: about 80% of VTI's weight by market value is in large-cap stocks — the same companies that make up VOO and SPY.
The ~20% that is mid, small, and micro-cap does add diversification — you own companies like those on the Russell 2000 and even smaller names. But historically, this extra slice has contributed very little to long-term outperformance versus VOO. In some decades small-caps have crushed large-caps (the late 1990s). In others they have lagged badly (the 2010s, when mega-cap tech drove returns).
The academic literature calls this the "size premium" — the idea that small companies earn higher returns over time. But whether it exists in practice, after taxes and transaction costs, is hotly debated. What we know for certain is that the difference between VOO and VTI over any given multi-decade period has typically been less than 20 basis points per year — and sometimes VOO has actually outperformed.
The practical takeaway: if you are choosing between VOO and VTI purely on expected returns, you are splitting hairs that may not even exist in your after-tax reality. The more meaningful decision is whether to pay 0.03% (VOO/VTI) or 0.09% (SPY).
Who should actually pick SPY
Let's be clear about who SPY is for, because it is not "everyone who wants S&P 500 exposure." The case for SPY rests on two specific use cases:
1. Active options traders
SPY has the deepest, most liquid options market in the world. Bid-ask spreads on SPY options are typically a penny or less. You can enter and exit multi-million dollar option positions without moving the price. If you trade options regularly — especially weekly expirations, spreads, or complex strategies — SPY's liquidity is not just convenient, it is essential. No other ETF comes close.
2. Large intraday traders
With ~72 million average daily shares, SPY can absorb very large market orders with minimal slippage. If you are moving $500K+ in a single trade and need to minimize execution cost, SPY's volume gives you an edge over VOO (~7M) or VTI (~5M).
If neither of these describes you — if you are buying once a month and holding for decades — then SPY's 0.09% fee is simply paying more for the same index exposure. In that case, VOO or IVV at 0.03% is the rational choice.
Verdict
| If you are… | Pick this | Why |
|---|---|---|
| Buying and holding for decades | VOO | Cheapest, simplest S&P 500 exposure. No reason to overthink it. |
| Trading options actively | SPY | Unmatched liquidity and options depth justify the higher fee. |
| Wanting total U.S. market in one fund | VTI | All U.S. stocks, all caps, 0.03% fee. But ~80% overlaps with VOO. |
In three sentences: VOO is the best default for buy-and-hold investors because it gives you S&P 500 exposure at the lowest cost with maximum simplicity. SPY earns its higher fee only if you actively trade options or move very large intraday orders — otherwise you are paying triple for the same index. VTI adds small-cap diversification that sounds appealing but has historically contributed almost nothing to outperformance versus VOO, making it a nice-to-have rather than a must-have.