Exchange Traded Funds (ETFs) have become as ubiquitous to investor portfolios, including retirement accounts, as their cousins in the mainstay mutual fund universe. Yet, few are apprised of the differences between these two asset classes. ETFs often have lower costs, are more tax efficient, and can be shorted (much to the delight of Mr. Chanos), while mutual funds may offer greater investor protections under the Investment Company Act of 1940.