IM (very unskilled) O, you should think carefully when considering any other render engine if the primary focus of your images is Poser figures. That is even more true today with the newer versions of Poser with SSS and utilities like EZSkin. I'm fairly happy with SkinVue and I'm sure the newer versions included now with Vue are even better. I seldom do portrait or closeup images though and the environment is usually a significant part of the image.

With most other render engines, AFAIK, you're going to have to roll your own skin solution or look for something that works. I read comments a few years ago by some C4D users saying that Cinema is lacking in that area compared to MentalRay. There are utilities like Vreel Skin for C4D especially for skin. I don't know how the Lux translators handle skin and hair. Of course, absent a good translator, you're going to have to create your own shaders for clothing, props etc. as well once you go beyond bitmap textures. That is perhaps less of an issue since there are usually a lot of free and commercial shaders for architectural, automotive, environmental etc. purposes.

So I would say that you can't simply look at speed without also looking at the type of images you usually render and how much work it's going to be to recreate shaders, the added cost of add-ons etc. Are you going for photo-realism? Do you do a lot of postwork?

For an emphasis on human figures, Poser and DAZ Studio are good solutions for many people. If you want great landscapes with figures, you may choose Vue. If you want primarily arch/viz with figures then some flavor of VRay or any number of other programs may do the job. Unbiased fans can go with Kerkythea, Lux, Maxwell etc. Each has their advantages and drawbacks. The old adage, 'fast, good, cheap - pick any two' usually applies. Poser would be well served to make network rendering of still images easier. That would address the speed issue for some users.

"I'd like to see the renders of the typical Poser user who switched to rendering in C4D and suddenly started producing significantly better work."

I assume that's a rhetorical since it's kind of like asking to see the typical X user who switched to rendering in Poser (or any program) and suddenly started producing significantly better work. I understand your (and Vilters) point about using what you have. It's probably foolish to invest in something new without fully exploring your current tools. OTOH, a different application may be more powerful and even easier to use in some ways. So, rush to buy something - no, but try something, absolutely. In that sense, looking at what the best examples is the only way to see what an application is capable of producing. You still need to look at what it's going to take to achieve that level of quality to see if it's worth the improvement in terms of time and/or money.

"Democracy is a pathetic belief in the collective wisdom of individual ignorance." - H. L. Mencken