Why you have to? Gmax has an collada-exporter surely. I can give you some notes about blender
+ speed of development is really high
+ you will get each new feature by downloading a new version (download + unzip, no need of an installer)
+ no pay
+ blender has nearly the same possibilities like 3ds
-> Modeling, Animation, Post Processing, Motion Tracking, Sculpting, Texturing, Image Painting, ...
+ no restrictions in rendersizes
+ many supported formats -> every image format, h264, mpg, avi, ...
+ support for various architectures
+ many tutorials
- for beginners the interface is horrorful, but after understanding the concept its aweful (better then 3ds in my opinion)
- you have to understand model topology for making clean models, in 3ds dont need to
because of the fact that i'm a blenderian, i find more pros then cons. There are more reasons for using or not using it. Its your part to give it a try.