Why buy SPY instead of SPX?

Could you elaborate on why an investor might prefer purchasing shares of the SPY ETF over the SPX index itself? Are there specific advantages, such as lower costs, greater liquidity, or easier access, that make SPY a more attractive option for those looking to track the performance of the S&P 500? Additionally, how do the potential drawbacks of each, such as management fees or market impact, compare when considering the two options?