Several actively managed ETFs holding diversified U.S. equities are beating their passive, indexed peers so far in 2015. Columbia Large Cap Growth (RPX) delivered 8.8% gains year to date as of July 8. By comparison, iShares Russell 1000 Growth (IWF) was up 3.4%. RPX’s average gain over the past three years also beats the Russell 1000 Growth benchmark. So what’s behind its successful investing strategy?