Inventor excels at solid modeling, plain and simple. It's geared entirely towards mechanical drafting to the point that you can assign materials to an object and extrapolate info like weight, density, resistance and other attributes. It's second to none when it comes to it's use of constraints for drawing objects.
All that said, I'd never attempt to draw house plans in it. AutoCAD is, with enough work, capable of most everything that Inventor can do, but it takes longer and never does it quite as well.
Where in Inventor excels at one area, AutoCAD goes for breadth instead. It's hardly shallow, but because it covers so much, it can't work as well a program targeted at a specific area.