I can't be 100% sure, because in the US we have never gotten anything but Professional sat nav.

Aside from the screen sizes, I don't think there is much of a difference between the two. The interface may be slightly different, but then again when we had Business Nav in our 118i hatch, I didn't find it much different from Professional Nav. You still get Trip info (petrol stations, Car parks, etc...) and it should have voice instructions. Voice Commands are technically a separate option but I do not know about option bundles in Australia.