JustSid: How did you get to that statement? Did we figure exactly that out what Julz wrote, when we tried to actually create a voxel based engine?
Polygons are very fast a way to render Voxels hardware accelerated. The more restrictive but probably cooler way are volumetric textures or something like that which are quite well suited for some basic shader based raytracing and the software way usually means basic to more advanced raytracing or ray marching.