When to Composite Images in a Render?


So my current WIP piece (you can check it out on my profile if you want), makes use of Arnold for rendering and uses the aiPhysicalSky for lighting. The lighting itself is fine, event he sky itself is ok, but what I’m wondering is what to do about the black ‘ground’, or the black color below the horizon line. I’ve debated if I should try to actually model out an environment that gets rid of that entire black background or if I should try compositing something in.

In general, what I wonder is at what point is it better to composite images rather than model the environment? I had some trouble with this on another project, so I’m very curious what people’s opinions are.

Thanks in advance!