Of the 3, I've only used MeshCAM so can't really compare it.
Here's my take as it relates to MeshCAM:
1) Toolpaths are overall very good. I see some strange things with arc fitting, but to be honest, they won't detract from the finished part. And Cut3D doesn't even have arc fitting.
2) Who's definition? Plenty of hobbiests use it, but also plenty of people are probably making money with it. Keep in mind that MeshCAM was originally developed for one thing. To create toolpaths from meshes. There are better options if you want to machine solid models, but they'll cost 10x more.
3) It doesn't get much easier, and it now has a wizard to do a lot of the work for you, if you want super easy.
4) Very fast, even on my 5 years old PC. But, speed is very dependent on many things. Model size, tolerance setting, memory available, and processor all come into play.
5) Limited in file types, as it was mainly designed to import .stl's only. It'll also import .dxf's, but you may need to know your CAM program VERY well to be able to use .dxf, as MeshCAM can only read 3D face entities in a .dxf file. If you don't know how to get your CAM program to create 3D faces, then .dxf import may not work for you.
6) Definitely
7) MeshCAM is in constant development. Cut 3D development stopped years ago, when it was released.
RhinoCAM is not really in the same class as MeshCAM, so it's not really an apples to oranges comparison.