I've asked myself the same question, albeit while doing 2D geometry stuff.
The answer I found for myself was that if I was planning to write a larger library, with more functions and whatnot, go ahead and return the Point, or in your case the Coord3D object. If it's just a hacky implementation, the tuple will get you going faster. In the end, it's just what you're going to do with it, and is it worth the effort.
