Herbivorous molluscs represent one of the greatest grazing impacts on abundance and diversity of primary producers in benthic ecosystems. However, the effects of nutritional content of kelp species on the physiological rate of trochoid herbivorous snails inhabiting intertidal-subtidal environments are less well known. Here, we conducted manipulation experiments to compare the nutritional quality of two kelp species, Lessonia spicata and Macrocystis pyrifera, and their influence on the feeding behavior and physiological rates of the snail Tegula atra. Experimental results demonstrated that L. spicata had the highest nutritional value (i.e., high organic matter and protein content), and was the preferred alga, compared with M. pyrifera in a choice experiment. However, when the snails were raised with each of the algal species in no choice experiments, no significant differences were found. Absorption efficiency and oxygen uptake were higher for snails reared with L. spicata than M. pyrifera, but growth rate was similar. These results suggest that high metabolic activity was compensated by the high absorption efficiency of T. atra when it consumed the preferred L. spicata, which could explain the lack of relationship between preference and growth rate.