I seldom use a .40mm nozzle much anymore since I mostly do functional prints like these gears. I have found the .60mm nozzle is a good compromise for speed in printing, better strength, and good accuracy.

Interestingly enough, a .40mm will print nearly or as fast as a .60mm nozzle on Bambu printer in general. This because Bambu optimizes their slicer setting for the .40mm nozzle. What it does give up a bit is between layer strength. This is due to to the smaller contact area difference between layers. I can get the same strength with 2 perimeters using a .60mm that would take 3 perimeters with a .40mm nozzle.