Mmmh.... probably don't really understand the question ... one can't compare the 3D needs to another ... they're totally individual ...

For the images, you are rendering (looking through your gallery) i clearly can tell, that DS3 alone or Poser alone is the right program for you. To create your style of images, you definately don't need more than that.

But for the variety of the 3D images i do, this can't be done with DS3 or  Poser or Vue alone. Impossible !
Many times i need vast landscape areas with many varieties of plants, reality like atmospheres, clouds, haze, special watereffects  ... and much more ... and DS3 can't produce something like that - only use just basic, pre-prepared stuff.

Like ShawnDriscoll already said - there are things that can't be done with Vue and there are things that can't be done with DS3 / Poser. So a combination of different programs IS necessary, to get the wanted results - if they are wanted ... in your case and your 3D scene style - DS3 alone is good enough ...