I can't speak for anyone else but literally the only reason I stick with using poser is that I've spent so much time using it and learning little tricks and stuff. Honestly if I were just getting into this and I had to choose I would probably pick DS because it's free and the public marketing is more widespread. I see a lot more advertisements for DS than Poser. But DS isn't REALLY free, it's a portal to a store after all. Poser also seems more transparent to its inner workings, but that seems to be diminishing for various reasons. Not least of which is the shrinking knowledge base. If literally only a handful of people can tell you how to use a feature of a program it's problematic. But these are content creator features and by it's nature most people using Poser and DS just want to use pre made content and render.

That being said, at this point I wouldn't invest any time learning either program and would suggest getting a more complex software like Blender or one of the other paid professional softwares and learning how to make stuff of your own. In the end I think it would artistically be a better investment of time. The best art is made by accepting, adapting, and pushing your limitations. It's how a style is developed. If I were an outsider just starting to look at Poser and DS art I wouldn't be able to see any individual styles. Everything looks the same, and that's encouraged most strongly by people here on the forum. And the nature of everyone using the same content. And render formulas. You MUST look a certain way otherwise it's not correct or it's not serious or whatever. As someone who's spent time in the traditional art mediums I don't think I've ever encountered such an "in the box" attitude. Anyway, I have a lot of thoughts on that topic, many of which are difficult and tiresome to frame into text, leading to more questions, plus it generally just pisses people off as far as I can tell. So why bother attempting to discuss it.