Yahoo Finance analysis indicates that while both the Vanguard S&P 500 ETF (VOO) and the Vanguard Growth ETF (VUG) are cost-effective, high-quality funds, holding both simultaneously may not achieve the desired diversification. The analysis states that the stock overlap between these two funds is as high as 57%. For example, NVIDIA and Apple combined account for 25.4% in VUG and 14.6% in VOO. This means investors might be over-invested in many of the same stocks, thereby increasing risk and reducing diversification. It is suggested that investors choose one of these two funds and consider complementing their portfolio with other assets such as value stocks, small-cap stocks, or low-volatility strategies.