For NDX100 since 1972, the marketcap has performed better than the equal weight, not worse. Note, for the SP500 this is reversed. The SP500 equal weight has performed 2 times better than the marketcap.

True, but the largest weighted firms in the Nasdaq 100 have not (historically) been pretty much the exact same list as the largest market cap listed firms in the US as is currently the case give or take, so the general rule may still apply these days when it's almost precisely the same top N. Or not...it's unpredictable, just a statistical skew.

As an aside, just a reminder that QQQ isn't market cap weighted. Which is sometimes better, sometimes worse, but yet more randomness.

To me it's plain as the nose on your face that it makes no sense to buy a fund which is hugely overweight a few stocks unless you think you personally have a very good reason to be overweight those specific stocks at their current valuations. I guess 2001 is a long time ago--it's a dwindling population of current investors who remember their investments' behaviour the last time the market was this concentrated in a few "can't lose at any price" names : )

Jim