draw vs update for many objects

This is more of a theoretical question. Say I had a huge number of points on the screen. I could either:

  
  
void testApp::update(){  
    for each point {  
        movePoint();  
    }  
}  
void testApp::draw(){  
    for each point {  
        drawPoint();  
    }  
}  

or

  
  
void testApp::draw(){  
    for each point {  
        movePoint();  
        drawPoint();  
    }  
}  

I understand that it’s beneficial to separate the two routines movePoint() and drawPoint() in case movePoint() slows down the draw routine. But I have seen the second method in some examples. Maybe in that case it would take longer to loop through the collection of points twice, once in update and once in draw?
I guess I’m wondering if there’s a general rule of thumb as to how much updating to do in the draw routine, perhaps based on the number of objects to update. Is there?

here is a good answer:
http://forum.openframeworks.cc/t/update-vs.-draw/776/0