Sculptris has great editing tools that allow designers to concentrate on sculpting and completely immerse themselves into making models, forgetting about all the complex methods modelers usually have to use in their daily business.
Sculptris is not primarily geared towards 3d painting, but rather sculpting. It also is not designed as a top of the line tool, but as a simple intuitive introduction software. This means it is a bit lacking in simple features, such as an eraser tool.
Although 2048x2048 is plenty for most indie developers, the lack of 4k support is definitely be a huge draw back for models that require larger textures.