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?
How reading the file from the file-system can affect performance. Often there are various ways to read a file in a programming language.

The physical transfer that uses everything below OSI layer 6 can't be different, as those apps all use Androids default APIs to achieve that.

Then how saving the file into the receivers file-system also affects performance. There are various ways to save a file in a programming language.