I can see your point, but in my studio we are typically showing 2-3 final concepts rendered out in 3D. To fully define three models is very time consuming, and ultimately a waste of time for 2 of the design directions. Having said that, you are correct that any big changes to your design modeled in Rhino will take more time as it will require a rebuild.
I agree that Fusion 360 has a lot going for it, and we did buy it for our studio to evaluate. The big problem is, we are always under a time crunch, so we almost never have the extra time it would take to model a design in a package we aren’t familiar with. We are chipping away at it slowly, and Autodesk have been amazing in offering support and free onsite training. I think they will definitely be growing their base in the next few years.