If all file sharing apps like shareit, xender and SuperBeam uses wifi technology to transfer files, why their transfer speed differs?

I've downloaded several file sharing apps like shareit, xender and SuperBeam. They all use wifi technology to transfer files. Then why does their speed differ too much. I've noticed that shareit takes 3-4 seconds while SendAnywhere takes about 30-35 seconds to transfer a same file on same devices. What makes ShareIt efficient over SendAnywhere?