If you're after the so-called film-look, 24p with 1/48 are the way to go.
With the shutter-speed you not only change the brightness of the picture but also the motion-blur. Faster shutterspeed = less motion-blur = more "strobing" motion.
If you want to maintain a constant look throughout your clips, don't touch the shutterspeed but change the brightness with the help of ISO, aperture or nd-filters.
A general rule of thumb is: Shutterspeed = 2 x fps
But: Playing around with shutterspeed can be a creative way to change the feel of a film. If you think about "Private Ryan" or the battle scene in "Gladiatior" (to take the best known examples), they are shot with higher shutterspeeds and have a kind of hectic feel about them.