@ bobby: Exactly

My initial reason for setting 2 judging categories was that Bryce 6 has some advantages over the previous versions, thus Bryce 6 entries will only be judged against other Bryce 6 entries, and the same for previous versions.
So, whatever Engine your final image is rendered in, regardless of the models you use or what version you created the textures in, the Final Factor is the Rendering Version.
I've created B5 files, re-rendered & tweaked them in B6, then rendered them in B6. These would fall into B6 judging.

The Subject matter (Content) matters not in the judging, it's only the theme.

I thought Frans question was pertaining to subject (theme) matter. Old Ring+a new Weddingdress, that sort of thing. Please correct me if I misread this.

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Ockham's razor- It's that simple