Yeah performance is big on this tool.

Voxels on 3D Coat, allow to do any type of operation on volumes in real space, but Voxels are lot more slow, if you increase resolution of voxels to one or two steps, you can't use big brushes only small, or it's too laggy, too slow to be able to work correctly.

With Z Spheres 2 , you can now do any type of form, and with the new brushes and features, you can do easily hard surfaces.

Zbrush only needs the retopology and texture paint features of 3D Coat