Software and product quality

I want to design and order some simple objects to be made via plastic injection moulds. From what I’ve read there can be huge differences in the quality of product that can be expected given the software used, be it parametric modeling software like creoengineer or autocad (or at the bottom, blender). It makes sense to me that there might be a .5 mm difference here or there between a between a product designed by freeware and one designed by autocad, but what would the difference be, if any, between product designed with autocad and one with a parametric modeling program like creoengineer?

And if I just want to make a some toy figures with a couple movable parts, what would be the simplest software I can use and have at most about one dud figure in 100? I’m prototyping on a makerbot if it matters–I would assume they only have a certain level of precision as well.

Anyways, thank you for your time.