Diverse companies really are better---well that is the case that was proved by McKinsey and Companies 2015  Why diversity matters report.

According to the report, while diversity in companies (specifically in leadership roles) is more of a correlation versus a casual link, the results which where based off of an analyst of 366 global companies, one can conclude that divers companies win by attracting and retaining top talent, better employee engagement, better decision making, and closer understanding of customers. This directly impact the business financially. 

Check out the McKinsey & Co. report...it's worth a read.