For now at least, human stock pickers are making a comeback against the overall market and rivals who just aim to clone its performance.

Through the end of April, U.S. stock mutual funds that are actively managed rose 2.25%, including dividends and expenses, according to research firm Morningstar Inc MORN, +0.40% Mutual funds that track various stock indexes were up 2.2% in the same period, while the S&P 500 gained 1.9%.

And nearly half of the mutual-fund managers who research U.S. stocks before they buy or sell, often holding on to investments for months or years, beat their benchmark through April, up from 21% for all of 2014.