A 300 meter sprint compared to a 300 yard shuttle. Roughly the same distance, yet vastly different in the effects. Sprinters will often perform 300 meter runs in workouts, without the detriment to speed (total volume and rest pending). Team sport conditioning coaches will administer 300 yard shuttles, and deter speed.
The difference is confinement. The shuttle format changes things.
The 300 yard shuttle
I am guilty of administering 300 yards of running in the past, but more guilty only by the way the runs were performed. A 300 yard shuttle at 25 (or 50) yard lengths with either 11 (or 5) turns changes the outcome tremendously. Not only does the duration of the run change from something in the mid 30 and 40 seconds to upwards of 50 to 60 seconds, but the musculature involved goes from the hips and back of the thigh in straight line, to the muscles on the front of the thigh. In a 300 yard shuttle with the many changes of direction, the separation of the hips is often less (decreasing range of motion), and the large volumes of lactate/H+ accumulation seems to 'stick' in the body's memory, holding the front of the thigh muscles tight for long after the run(s) have finished.
Consider this for any distance of runs; administration of "150's" in track vs. "150's" in field or court sports.
Variables of different runs
Distance and time of a run matter, but it's the total amount of space given to do the run that really speaks in different ways to the body. Tight spaces equals more front of the thighs, and open spaces more back of the thighs. The ground contacts are usually longer in tight spaces, while shorter in more open ones. The tight space, shuttle format, if trying to match distances of 100 meters plus, ends with the athlete looking like their tires have gone flat. The finish of a straight line run is usually a heck of a lot faster than the shuttle runs.
Anything that hurts running mechanics, is likely to hurt speed. Look and run fast
The other aspect is rest. I think a longer sprint/run is fine for a sprint athlete, in an attempt to push the conditioning window a bit. A linear (or curvilinear) 300 meter run would be possible if the athletes have developed running skills and are given a good amount of rest between reps to maintain those running mechanics throughout (the body is always adapting). Like I alluded to above, longer runs seem to "burn" into the body's posture and patterns more definitively, and with the way shuttle conditioning is prescribed (many turns), it usually doesn't enhance the posture and patterns a coach would look for many of today's bound-up athletes. The shuttle format creates a lot more intermediate level work, and requires a lot of energy to stop and overcome inertia repeatedly - there's not much for fast accelerations or velocities.
Personally, I am more comfortable with getting into zones of work that are outside of true speed and power, but only if it's with the longer, straight-line runs. I would much rather have athletes feeling the burn in the glutes and hamstrings, than the oft-overused muscles in the front of the thighs and hips. Certainly not too much of this work, but over time the longer sprints can work as a 'fix-up' for the student-athlete that spends a large majority of the day in a seated position.
An interesting side note to this, I suggest looking closely at the athletes' postures and gaits after performing longer sprints 50+ meters (so long as they were quality, because of adequate rest times and fast speeds)... from what I've noticed, they stand taller, with the shoulder blades back and relaxed down, with the front of the hips open, and the pelvis set nicely and flowing (nutation/counter-nutation, and rotation about the transverse axis) Quality, fast running seems to 'wake-up' the body.
Soccer coaches will use different size fields to practice different technical and tactical skills. I see the field changes as different stresses on the body, as discussed above.
It's not that the small space shuttles don't have their place... they can be used for the conditioning aspects discussed above. I just find it important to look at all the details of the physical actions of different runs, not just the measurables of distance and time. All movements strengthen the body, just in slightly different ways.