AutoCAD is designed for building mechanical parts, electrical schematic boards, Architecture drawings, civil drawings, etc. Autodesk purchased Revit Technology Corporation for $133 million in 2002. The software is specifically designed for building 3D Architectural spaces. Revit is a very advanced compared to AutoCAD. Your model is created in 3D with the help of families that are designed to help create a house in minutes. Revit has parametric capabilities which helps the Architect count doors, windows, walls, furniture, trees, automatically. Drawings are super easy to create and all the views are related to the cross sections automatically. Revit also has structural capabilities that allow you to create a foundation as well as the structure connections in minutes. MEP is also integrated in Revit allowing you to create these parts in 3D. This helps to see if you are hitting other objects with the use of clash detection.
As you can see Revit is AutoCAD on steroids. Once you switch to Revit you will never go back to AutoCAD.
Good luck with your venture using Revit.