Oh dear !
You cannot compare a Cocolino or Topolino3 or whatever it is called to a simple adapter ! Why do you think it is so expensive while you can get a simple 6pin mini-din to 9pin d-sub adapter for a few bucks ? The Cocolino is not an adapter. It is a complete micro controller residing inside the case of an adapter. It understands PS/2 protocol and translates it into joystick impulses as needed by the Amiga. It works with any mouse which supports the PS/2 protocol, be it a PS/2-only mouse, a PS/2-serial combi mouse or a PS/2-USB combi mouse. It does not do any serial transmission and it is not able to tell the Computer which PS/2 codes it received from the mouse.
Bye,
Thomas