Yup. When someone is looking for the 'Best', they are really looking for the best implementation of ModuleWorks. One thing I want to add to this, even though MW drives the backend calculations, you can still implement the technology poorly. There are a few companies that do their own toolpaths that I found when I did a CAM system evaluation recently and those are Esprit, Hypermill, and CamTool. I'm sure there are more, but I was only looking at Top Tier CAM systems. Esprit does license the MachineWorks kinematics simulation, and Hypermill licenses Volumill like Camworks does. But other than that, they do their own toolpaths AFIK. In a comparison of toolpath generation times on a seemingly simple part using dynamic roughing or volumill, Camworks took hours, Mastercam 45 mins, Hypermill 10 mins, CamTool 1 minute. All for the same or similar toolpath. If Camworks and Hypermill both use Volumill, why is Hypermill so much faster? Well, the licensed software is implemented and utilized better.
I think why Mastercam is held in such high regard is because it's implementation of Moduleworks is better if not the best. I've demo'd it over the course of a few weeks, but never became proficient. I saw a lot of really useful tools. But like you said, it's often more about what people prefer and are used to.