This review points out the problem of processing multiple sensory inputs and provides evidence that generalists suffer a disadvantage compared with specialists with respect to efficiency of host plant choice and discrimination. The specialists' mechanisms for improved efficiency are discussed as well as some of the processes that may be selected to increase processing efficiency in generalists. The fitness consequences of differences in efficiency of specialists and generalists are pointed out. One of the major disadvantages for generalists is the increase in vulnerability to ecological risks, especially risks imposed by various natural enemies. Efficiency-related factors are indicated as previously underestimated elements that could influence host affiliations including diet breadth and changes in host plant use.