MS3D: Simple, costs money, can do everything possible model-wise in Blockland
Blender: Complicated, free, can do everything possible model-wise in Blockland
If you're cheap get Blender, if you have like 40 bucks to spend on something get MS3D. In the end you can utilize all of Blockland's possible model functions and things using either program so after that it only depends on whether you want to scratch your head or throw money out the window.
Here's an old chart featuring exporter can-dos and can't-dos, I figure both Blender and MS3D can do everything on that list just fine now.
http://alexswanson.com/torque/dts/
