SPDR S&P 500 ETF Trust (NYSEARCA:SPY) and Vanguard 500 Index Fund ETF (NYSEARCA:VOO) track the same S&P 500 index. The real contest is structure, cost, and cash flow. With the VIX at 17.39, this is a clean moment to compare them. Same Index, Same Names at the Top Both funds own identical holdings. SPY’s largest ... The Hidden Drag of SPY’s Outdated UIT Structure: Why VOO’s 6.45 Basis Point Fee Advantage Matters Over a Decade