Does it matter if I check collision of a GraphicsItem to every other item in a scene or if I check collision of an item against the parent of these items?

Ex:
Option 1:
Qt Code: 
  1. QGraphicsItem generic1;
  2. QGraphicsItem generic2;
  3. [...]
  4. QGraphicsItem generic30;
  5.  
  6.  
  7. QGraphicsItem mainItem;
  8.  
  9. mainItem.collidesWithItem(generic1);
  10. mainItem.collidesWithItem(generic2);
  11. [...]
  12. mainItem.collidesWithItem(generic30);
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Option2:
Qt Code: 
  1. QGraphicsItem genericItemParent;
  2. QGraphicsItem generic1.setParent(genericItemParent);
  3. QGraphicsItem generic2.setParent(genericItemParent);
  4. [...]
  5. QGraphicsItem generic30.setParent(genericItemParent);
  6.  
  7.  
  8. QGraphicsItem mainItem;
  9.  
  10. mainItem.collidesWithItem(genericItemParent);
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Which one is faster?