ETFs provide investors with a sophisticated tool that lets them invest like professionals. They’re liquid, less expensive than mutual funds, and they can mirror indexes, which helps investors optimize portfolios. And since they’re a hands-off investment, ETFs allow investors to spend more time focusing on asset allocation.Investors can use ETFs to hone their asset allocation decisions by targeting asset class subsectors.  Except for the few that are actively managed, most ETFs have well-defined targets that are quite transparent. And due to small variances among similar ETFs, picking the best ones should be simpler than choosing a mutual fund.