Point or Flex

Ok, so I've been wondering about this lately. When doing any kind of leg lifts, donkey kicks, inner thigh, outer thigh. What is the difference between flexing the foot and pointing the foot? Is it better to do one or the other? Does it work different areas based on which way the foot is? I've tried switching back and forth between the two I don't know that I could tell a great difference, but I am curious is one correct or incorrect as far as form? Or is it personal choice? I know Kelli mentions point toes for extra credit in some of the workouts I've done. Anyone know?