Investing is a way to grow wealth over time—but building a business is the quickest way to wealth. 

Building a business takes a lot more time each day, but builds wealth more quickly. 

Investing (index funds in the stock market) takes years to grow wealth, but takes very little time day-to-day.

If you have lots of time each day, build a business.
If you have lots of time (years) before you need money, build a portfolio.