I had to think for a minute about Louis’ comparison of Ollie’s and Ken’s scenics and here are my initial observations:
Ollie’s are solid polystone and very heavy. Ken’s are foam. Polystone can break, foam can warp. Foam is cheap to ship; heavy objects are expensive to ship.
Ollie’s stone walls are multi-colored, Ken’s are more uniform.
Ken has complex models with windows, doors etc., Ollie’s are simpler and doors etc are not functional.
I think both are meeting 1/30 scale and are generic enough to be used in large parts of Europe. I would use the simpler of Ollie’s buildings starting the 15th century, Ken’s several centuries later because of the use of mass produced brick (subject to debate).
Damage to the buildings is severe and I would not use any damaged buildings from either Ken or Ollie before 1914.
This all is of course highly subjective.