It is a very common question in architect and construction professionals whether I should learn AutoCAD or Revit. To be honest, this is a very interesting question. But AutoCAD and Revit are completely different software with different purposes.
AutoCAD is pure drafting software while Revit is used for Building Information Modeling (BIM).
AutoCAD is good for creating 2D drawings manually while Revit is a 3D modeling software. Revit goes into great detail to create accurate 3D models. Revit is also used for other purposes such as design, documentation, estimating and costing.
Revit is a powerful 3D modeling software in which drawings are correlated. If you change anything in the plane, it will be automatically reflected in the elevation and section drawings.
In AutoCAD we have to manually convert each drawing. Architecture and design engineers must have knowledge of both the software to make their work fast and error free.
If I talk about the learning difficulty, AutoCAD is very easy to learn while Revit takes time to understand the workflow. Learning Revit required a completely different approach.
Some people try to work in Revit the same way they do in AutoCad. We should avoid such approach while working on Revit.