The equal weight index is the winner over the cap-weight index on both fronts, so RSP isn't too bad as a one-ticker portfolio.

We'll have to agree to disagree, and that's fine. You do you. Be happy in RSP, and avoid index funds.

As for us - meaning the vast majority of American investors - the reasons why index funds are better for us are:

1) We can't even find RSP as an investment option in our 401K retirement plans

2) We have our capital in index funds compounding tax free in our 401ks. RSP in a taxable account would incur taxes on dividends and sales.

3) RSP had worse drawdowns compared to an index fund in every single bear market since 2003. For example, it was down 30% in the recent 2022 bear market compared to 27% for an index fund.

4) An index fund delivered a better risk-adjusted return compared to RSP over the past 20 years.*

5) Index funds have about 1/4 the expense ratio of RSP. We're cheap. We like that.

* I measure risk-adjusted return using the Sortino ratio. The Sortino ratio is calculated by comparing an investment's average return rate to the risk-free rate, and then dividing the result by the standard deviation of negative returns. The higher the Sortino, the better the risk-adjusted return. Below are the metrics over the past 20 years.

SPY vs RSP over past 20 years (since 2004)
      CAGR   Sortino  
SPY   9.41%   0.87    
RSP   9.36%   0.79