Normally a Minute Repeater has the strike function integrated in the movement. So usually you see the hammers and gongs from the back of the watch. The con of these movements is that they are rather delicate and require a huge amount of fine adjustment.
The IWC MR is different since it has a modular system.
One of the big advantages is that the whole system seems to be very robust and reliable. I wear mine often on a daily basis and can do nearly everything with it (except swimming or diving of course).
The main draw backs are that the strike mechanism is obscured from view and so the sound is not as loud as compared i.e. the JLC MR (that Nico owns).