I worked with Blender for a while. It's true, you can get results and have a quite good workflow - but the UI is more of a power-user-friendly interface than anything else. I felt it being terribly un-intuitive, even more if compared to C4D or Maya, etc.
Sculptris can't be compared to it, because it is very limited. On the other hand it has a very intuitive interface.
Can't check Autodesk 123D, but will asap.