Hi Ben,
This is perhaps a longer discussion, and no-one might have the perfect answer, except for bigger is better as it can’t hurt (excluding the budget)
Typically you have six areas to work in CINEMA 4D: modeling, texturing, lighting, camera, animation and rendering.
Where is your main part? Each has certainly different requirements on the Hardware. How large are your objects? What format do you want to render, SD, HD or UHD, perhaps mainly for print? Questions that I do not ask you, questions you have certainly already answered. Nothing I need to know, I asked them more to make you analysis your filed. Each part has more or less a different demand on the hardware.
The bottom line for me is more, can you work organized or is your work style more—dumb all in a scene, have everything oversized, like mesh-resolution and amount of lights and let the computer figure it out? I work most of the time on a laptop, not even the newest one, all Mac here. But I’m coming from a time where the computer had 1/1000 or even less power. I rather set my lights carefully than hoping GI will figure it out. I try to get an efficient mesh, and enjoy the elegance, than using dense set ups, etc. If something is to my liking, I move the file to my octo, and render it, with the laptop free for new creation. I build and explore set ups as small as possible. Yes it is tempting to start with the final version right away, but it slows down the creative process, independent of the CPU/GPU.
Some parts can’t use more than one core, so a twelve core is waste sometimes. Most stuff can use it, so more cores—faster results.
I will not suggest any hard ware here, I guess the flood of individual questions will overrun me if I ever start this.
My advice is, have the “activity monitor” for a typical week open. Check when your work slows down, if the memory is used completely, if the CPU has trouble catching up etc. All parts of that will give you clues what part needs for your specific work the largest, best or fastest. SSD of Raid perhaps. Hardrives can slow specific work a lot.
One more example, your set ups might be small, but the renderings might be intense, which would lead more to a render-farm set up, than intense models with very little render effort. As much variables this has, as much answers there might be.
In any case, the rule of thumb is, what you have to decide now or later is important. What can be changed later, updated or added to your Mac. Some parts are easy to change, some are not at all.
What else do you do? Is your post production heavy or small?
I hope I was supportive enough to make you feel more safe to decide, but I can’t and won’t name specifics here, I hope that makes sense.
All the best
