Hi Vrauckis,
So far I can tell (working on film, as well with and for film artists since 1989)—it always depends. There is no fixed rule. Each project has its own challenges and advantages.
Please keep in mind that the precision that C4D uses theses days is much higher than in the old days (Well, you might remember in v4 (or v5?) that there was a double precision version on the CD already… ;o)
In film, compositing is the key. You nearly never have a complete scene and render all at once. If you have to have planet earth in the background, it might be just footage (practical or rendered, or based on matte-painting.) However, the greater the distance to an object is, the less a small detail or parallax concerns count. In this way camera projection is mostly in use, and/or just digital matte painting. A key thing to understand in film is that we produce an illusion from a very specific perspective. In film you build and produce only what you need: Nothing more. It is on the end something that should produce money, and not burn it down, just because it is cool to have a complete model for all cases.
Film means to me to figure out if a practical shooting on set (or location) is preferable over a miniature or maybe a 3d model. Maybe a mix, maybe not. It all is a question what you need. All of that is a longer story, and there is certainly no “rule” or “one size fits all” procedure. Money and time is certainly a stronger factor in the decision than anything else, except you work in independent film, then no money and all the time in the world is your budget (Book: Stu Maschwitz, DV Rebel) The mix with practical miniatures will introduce the scale discussion automatically. Math is then a needed component in the mix.
What I found to be tru is that the target of it is the “key” and the way to get it done is the challenge to solve. What ever pleases the eye is key. How to get it, is the challenge.
Scale, the earth can be projected, or done separately. I don’t think at any time it is a wise idea to have human scaled (space located) object as main foreground and have an incredible huge sphere-boject in the background, because “one” likes to work in one scene. In film, as your question is, it is most unlikely that the artists working on the space-station are the same who will work on any back ground material.
Check out Cinefex (a must have subscription for VFX artists) and of course watch any “making of” you can get your fingers on. (I collect movies for that purpose, it is a four digit number already)—will say, the learning never stops.
Film means to me, to know the capture and compositing part as we’ll, if one likes to be a successful 3D artists. Not knowing the steps before and after (3D) puts the artist in a claustrophobic position.
Knowledge and experience delivers the base to explore the next project and as an result, to find (hopefully) the most efficient way to get the current shot done.
All the best
Sassi