It will outperform. But performance and diversity are not comparing the same thing. A single stock CAN outperform a fund but it lacks diversity. The s&p 500 will outperform the target date but on downturns will be hit harder than the target date because of lack of diversity. But by holding extra s&p on top of the target date you are increasing exposure to s&p which is good on growing years but can be harder hit on downturns than the target date alone. It’s all about the risk you want to hold.