I agree, there does seem to be a persuasion to have ZBrush with Sculptris in mind. Zbrush is neat but for a market based on real professional work and studio use.
It has been a while last i looked at 123D Design. Worth investigating again. It looks like it might work for simple organic shapes.
Wings i have not looked into for a very long time.
TopMod3d looks to be the most easy to understand judging by it's UI but there are plenty of others on that list. However, some of the UI's look old and messy, CAD modeling could get complicated though.