Milkshape is free for the first 30 days, I recommend trying it first before you make a decision.
Each has its pros and cons.
Blender has a wider range of moddling toold and hard interface.
Milkshape is very easy to learn but limits you in it's interface in trying to create a low-poly, but decent object.
So much truth.
Blender is much better for making models look nice, especially auto-filling faces, extruding, and beveling. Milkshape is much better for vertex manipulation, creating basic shapes, as well as having lots and lots of advanced config and tools.