Should you invest in SPX or SPY?

Are you considering investing in either the S&P 500 Index Fund (SPX) or the S&P 500 ETF (SPY)? Both offer exposure to the top 500 largest companies in the US market, but they differ in structure and costs. The SPX is an index that tracks the performance of these companies, while the SPY is an exchange-traded fund that aims to replicate the index's returns. The SPY has a lower expense ratio, making it a more cost-effective option for investors. However, the SPX can be used as a benchmark for other investments and provides more flexibility in terms of derivatives and options trading. So, should you invest in the SPX or SPY? What factors are most important to you when making this decision?