No, this is a very simplified way to view things. Another similar myth is: If you throw more cores at it it will go faster. The speed depends on the slowest component, or bottleneck, which is mostly on the CPU for blender. Obviously zBrush coders are really good since they’ve managed to squeeze so much performance out of the CPU only. We do use some tricks as well but blender is not a specialized sculpt software and keeping the sculpt part consistent with the rest of the program has its own set of costs and limitations.
Blender sculpting is really 3 systems: Mesh, Multires and Dyntopo sculpting, each with its own performance characteristics.
I assume when we speak about zBrush vs Blender we speak about multires sculpting. While multires is indeed slower and buggy, we haven’t spent too much time optimizing that part of blender really.
To recap: viewport is not really about tool (sculpting/painting) or animation performance, it’s about screen refresh performance (panning, number of triangles on screen) and appearance (shaders). Currently I am mostly focusing on really problematic display code of blender, such as subsurf and probably edit mode as well. All in preparation for the shader based viewport we will be making.