Another minor point on "flopping" corners or always having a guy play a side. When you always play the same side, it's less tiring. You get a break here and there when you have the skinny side of the field to cover. The other point to not flopping is consistency. Your mechanics are the same when you are always playing the left side or whatever.

There is no right or wrong to this question as it's debated at coaching clinics, etc, as to the superior method.