Go Big or Go Bigger: Is the Vanguard Mega Cap Growth ETF or S&P 500 Growth ETF the Better Buy?

Vanguard S&P 500 Growth ETF (VOOG) is recommended over Vanguard Mega Cap Growth ETF (MGK) for long-term investors. While MGK offers a slightly lower expense ratio of 0.05% versus VOOG's 0.07%, VOOG's broader diversification across 148 holdings versus MGK's 56 holdings has delivered superior returns across most time periods, with VOOG returning 22.80% over one year compared to MGK's 18.80%.