As the name implies, Studio-I is specially designed for the high sensitivity, low impendent earphones. Studio-I has a more high end circuit design. It has more highs and bass extension. The bass is much more comfortable and 'real'. The sound definition is much clearer, with the highs, mids and bass sounding just like you are present in the recording studio. Of course, the battery life of the STUDIO-I is longer than that of the STUDIO.
Studio-I is the best choice for hi end and highly sensitive IEMs. It can extract the full potential of high end earphones.