While value investors don't like the cap weight spx because things will get overvalued, it kind of acts like a momentum fund at times, hence TSLA. Warren has recommended the SPX since 1993 in the annual letters. Even back in the days of the partnership he made mention back then that the Dow index was a worthy competitor, and that is price weighted.

Me personally, I am selling pieces of Berkshire now and reinvesting those proceeds either in a stock I deem to be cheap and good, or the SPX index. If it's good enough for Warren, it is good enough for me.

To me the RSP is a contrived index, its not reality of the world. It sells everything down each quarter to an equal weight, goes counter to Warren's and any long term believer in businesses strategy. Isn't the object to hold great businesses forever? Why sell them down each quarter.

I know Greenblatt has said that the RSP beats the market by 2% per year, but that goes back, I believe to the early 2000's, like everything else starting point matters.

That's my nickels worth of thoughts :)