Simple question requires a simple answer. The longer the legs the bigger the stride which means the less steps to cover the same distance. When the arches have fallen from spending a lot of time walking, running and playing with no shoes on result is flat feet. When l went into the service one can not get into the service with flat feet.
Usually long legs. Long legs give you a better stride and people with short legs are slower kind of. If you are tall it should help. Hope my advice helps!