Frans, Thank you! This is great work and very helpful to the 3D printing community.

Thinner layers make for stronger parts.
In my experience a 0.15mm layer height with a 0.4mm nozzle gives the best tradeoff in print quality vs speed.
Imagine a cross-section of a 3D printed wall. The extruded filament comes out round with the width of the nozzle, and is compressed to the set layer height.
This leaves air pockets in between layers. With a 2x thinner layer, because the nozzle size remains constant, you get half the material in half the height, which means the filament gets compressed twice as much leaving half the air pocket. Because the filament is forming more or less a flatter ellipse, the area where the layers meet will exponentially increase (at least more than linear). Also the part becomes more homogeneous overall making for a much stronger part.
This has consistently been my experience.

@Frans, for your experiments n = ?