that depends, really
Blender looks daunting at first, because there a LOT of buttons
but it's very intuitive to use, once you learn to press spacebar (took me ages to find that one)
milkshape certainly looks a lot easier, and there's more tutorials for it (hooray for Jwoods

I've never tried Anim8tor, and there's also Wings3d, another free program
you can always try them all and see which one suits you best
for instance, I've heard people say how easy Wings 3d is, but never got past the opening screen myself
while some people have nightmares about Blender
oh well
