AutoCAD Architecture organizes helps organize individual drawing files together into a project. Changes to geometry occur in constructs. Documentation and detailing occurs in view files. Plotting arrangement occurs in sheet files. You cannot change anything in any view since it is a one way flow, semi-automated. Users must refresh the project. To collaborate, individuals are responsible for individual files.
Revit is a single file structure (except with linked and shared projects). You can change things in most any view they show up in. To that degree Revit is more BIMish than AutoCAD Architecture but they both work well on real projects. The training curve on AutoCAD Architecture is steeper but most users already have AutoCAD experience and so only the extra features of AutoCAD Architecture need specialized training. In my opinion, detailing is easier in AutoCAD Architecture and modeling and scheduling is easier in Revit.
It is possible to do a very bad job in Revit and a very good job in ACA and vice versa.
I strongly disagree that all parts of a project need to be on the same software. It should just look like its on the same software. I use AutoCAD, AutoCAD Architecture, Revit, 3dsMax. , GIMP, Adobe Acrobat, Premier Pro, etc. sometimes on the same project. The end result is what counts. Since I also prepare shop drawings, I see the end results of a lot of different A/E Offices, both small and large, and they almost always end up with PDF files of greatly varying quality, with some being very poor image scans even though you can tell they were done in BIM software. In some cases, I've found it easier to work with with good sketches than with CAD and BIM produced documentation.
Architect, Registered NC, VA, SC, & GA.