Midcap core mutual funds, which invest in both growth and value stocks, have outperformed the other midcap styles in the past 10 years. A $10,000 investment in the average midcap core mutual fund made on June 30, 2005, would have grown to $26,231 by July 10 this year, according to Morningstar Inc. The same investment would have grown to $25,736 in the average midcap growth fund, $22,632 in the midcap value version and $21,530 in the S&P 500.