The greatest advantage to adding large-cap stocks to an investment portfolio is the stability they can provide. Because large-cap companies are so large and have a well-established reputation with consumers, they are less likely to come across a business or economic circumstance that renders them insolvent or forces them to stop revenue-producing operations completely. Companies that are considered small- or mid-cap do not have the same level of stability, and therefore carry a greater degree of risk than large-cap investments.