I needed a DW that could take a custom door.  The 300 is one of the few models that accommodates a custom door.  It's on the lower end of the Bosch DW line, but works just fineand just as quiet as the 500.  We replaced a KitchenAid and the Bosch capacity on all three racks is far superior.  The big difference is that there is no heating element in the bottom.  Drying is through air circulation.  We just start it up and let it run overnight.  Love the red dot when it is running.  We no longer have to put a sticky note on the door.  We kept opening the door in the middle of the wash.