One thing to consider whould be how easy it is to actually learn to use.
3DS Max has arguably the most tutorials, ranging from beginner to the more advanced topics. Out of most software, I found the tutorials really useful when starting out.
3DS is also friendlier than Maya when it comes to learning as maya's advanced features are a bit confusing.
Compared to 3DS, the interface and workflow of Modo is a bit (lot) smoother and the community is a bit closer. The price is also a lot easier on the wallet. However, as Modo is comparatively newer, it doesn't have that many tutorials and there are less communities out there which use it.
The only thing stopping me switching from 3DS to modo as my main software is: the marking menus (also called radial menus) in 3DS Max. They are awesome.
pax.