The difference is most people either dont know how, or are unable to find a good mounting spot for their HDSI transducer to eliminate cavitaion at high speeds. Most people just add the y-cable and the high speed transducer, mount it and are done.
I believe both transducers have the same specs, just different shapes and of course the high speed only does 2d.
I’m strickly talking HBird transducers and not anything off brand.
What unit are you looking at a transducer for?