Watch how this user takes a basic low-resolution tiger model from Thingiverse and transforms it into a higher quality tiger head. I think a video illustration can better show you just how intuitive the Blender application. The flexibility that you have for creating models is second-to-none, where you have 20 different brush types, multi-res sculpting supports, dynamic topology sculpting, and mirrored sculpting, all tools to help you create. Mac users can happily use Blender without issues, all for free.
Blender is a great open-source app which specializes in 3D creations, namely sculpting for 3D printing, but it can do a lot more beyond that.
