Hi ed,
What I would suggest is to make a list of what features and aesthetics are important to you. Perhaps in hierarchic order.
To pay money for anything should be based on such reasoning. They are not all the same; otherwise it would be easy. Third-party-renders for Cinema 4D are on the market for a few decades.
Every once in a while, a new one shows up and has some features others do not have. Then others catch up or not. To give you a little bit of my digital background: I bought my first external render in 1994, RenderMan from Pixar, and two decades ago, I purchased Maxwell, etc.
I haven’t used any since way too long. I bought them at that time for different reasons. I would not invest in this if you have not made that list and checked if you don’t get that with the native renders right now.
Each renderer has a learning curve. Which is from my point of view the highest investment [your time]. The price nor subscription of such an app comes not even close to that.
So, make your shopping list, and what qualities you want to SEE in the final image. The only thing that I find otherwise interesting is the realtime response, as it accelerates your workflow. This time savings needs to be in balance with the invested money and time to keep this tool as a proficient knowledge in your toolbox.
I’m 100% biased, so to ask me is kind of dangerous. I tell you to use RedShift, as it will have the best integration at one point thinkable. Updates will be faster available due to the companies umbrella to own both. Again, I’m biased. I doubt that anyone has mastered all of them at the highest possible level. Besides being an owner, every single artist has his or her particular target with such a renderer. Are these congruent with yours is the question?
Specific error questions might be best addressed in the forum of that particular application. It is nearly impossible to keep track and updated with over a dozen of specific third party renders. I hope that makes sense.
As long as you can test and explore them based on your needs, you might save some money. However, the art of setting light and cameras, besides any other part in the scene, needs to be understood, so you can get an idea of what the renderer really provides.
Learn the native render that you can get great results from it. Then you can see what you really get on top of that from the 3rd party.
My best wishes, stay safe, stay healthy.
