Small was beautiful this week. The Dow closed above 15,000 for the first time on Tuesday, then held above that milestone for the next three days. But an index of small-company stocks put the blue-chip gauge to shame. On Friday, the Russell 2000 closed the week up 2.2 percent, more than double the Dow’s gain. Investors are in love with small stocks because they stand a greater chance of surging ahead than large, global companies do if the US economy continues to fare better than Europe and Asia. The Dow, the Russell 2000, and the S&P 500 all rose for a third straight week. Stocks have benefited from record-high corporate profits.