Always deeps questions Michael
Here are professional users who could give you much more inside about the death-line based art side of these things.
If you ask me it depends on what you want to archive.
Will you only make a nice-great looking video to show what you are able to do in the programs you use ;
then make it hard as it gets and some way you will find a the job you want (if it is for a demo).
But if you want only a nice-great looking video to tell a story then what does it matter what software or 3D -2D you used to make it ?
Make it in the fastest and easiest way without scarifying the vision you have.
If TG3 is a part of it use it. I can not give more specific answers without knowing what you want to do (in detail).
The scene above is a good example actually.
Does it matter if it is 2D or 3D beside us speaking about it?
It looks nice.
I for one will use TG3 wherever i can.
If it takes too long and another software is faster without much a different look i will use the other one of course.
There are others that use TG3 with objects very nicely for example but i still like using Lightwave in that regard.
So i would use comping probably TG3 with Lightwave.
I would make the city in Lightwave and would comp it or would use TG3 rendered backgrounds etc.
You remind me the way i thought 20 years ago.
I wanted to make this and that and this...but the computer took hours to render and could not handle all i trow at it.
I still do this sometimes today. I made a tree to test how to use 3Dcoat, lightwave, TG3
and a free Lightwave plugin (
http://dpont.pagesperso-orange.fr/plugins/Verdure/DP_Tree_Manual.htm )
and i crashed all of those programs constantly in the last 2-3 days.
I have 32 GB Ram but i saw more then ones out of memory kinda problems.
One tree was nearly 2 GB and no program could open it after i saved it etc.
I still try to make scenes that that have everything in one place .
These are mostly Terragen scenes. But mostly for fun if i can make them in Terragen or not.
But if you want to do this as your job that is a different thing of course .
For example first make a basic animatic Michael .
Do you have one? Or a storyboard Michael?
Then you can see better how you should approach this probably .
As i wrote below i don't remember cities scenes made with Terragen.
Others will help you more probably about this.