When I think of long strokes, I think of anything over about one inch (two centimeters). Although I confess that I'm prone to use long strokes when not shaving mindfully, I think they increase my chances of getting poorer results including weepers, nicks, and cuts -- mostly weepers in my usual experience.
Long strokes work best on stretches of skin that lack angles and depressions, which doesn't describe my face and neck at all. (My facial and, especially, neck skin is rather thin with lots of hills and valleys, dips, and corners.) If a person is shaving on skin that is, instead, rather fleshy, full, and smooth, then long strokes may work just fine.
Short strokes, being the compliment to long, are about an inch or less. These strokes allow for good control and frequent reset of razor angles as appropriate. When I'm using my slant razor, for example, short (and direct) strokes are the required technique. If I lapse into long, lazy swipes at my beard with this most capable of razors, I am guaranteed to draw a little blood at some time in my shave as the guillotine-like slant of the blade lops everything in its path -- including small bumps and ridges that may arise in my aggressive strokes.
Stroke length is somewhat akin to speed when parking a car in a tight space. If you drive too fast as you maneuver the automobile, you may encounter undesired contact with other objects before you can react to avoid them. Creeping slowly as you position the car allows better monitoring and control of the process, usually allowing damage-free driving. So it is with stroke length, where shorter strokes seem to provide better control in avoiding mistakes.
The ultimate short-stroke type is buffing, which is an abbreviated, back-and-forth sequence of razor movement on skin, in which each forward slide is slightly longer than the backward, thus allowing the razor to progress across the beard. This type of stroke is normally used for finishing a shave, removing the last projections of whisker to achieve the greatest smoothness.