Here was a small test. The project was stress test for all features made in 5.3, then with a bookmark I measured performance. Then copied the project(small in MB, large scene) and switch it to 5.4, same place, same resolution. Not a pretty scene but the performance speaks volumes. Most of the scene is below .4 roughness, very little quad overdraw, high (“60fps”) settings.
Could you do a path tracer render to see which one is closer to it?
did that in this post, but I can go ahead and do an archviz scene soon.
EDIT: Gezz, just realized Lumen GI doubled in cost(both had it in async by default).