What is considered a small hand for shimano?
You'd probably have to try it and see which is most ergonomic for you; even if you have large hands, the small hands lever may feel better. Older levers came with a rubber piece to stick in the brifter to adjust for smaller hands, but this has limited differences versus a different lever. 

Most females would fit into the small hands group. Younger males up to some age might as well. Adult males of average or larger size would likely not.