title: Use property in class extension instead of ivar in post ARC
body: <p>The recommended practice is to use property, including private ones through class extension instead of ivar (except in init and dealloc) in the post ARC environment.</p>
  
  <p>Aside from it being a recommended practice, what are the main drawbacks in someone using ivar instead of property? I am trying to convince some folks to make the switch but some have argued ivar works just as well and faster.  So I would like to collect good solid arguments rather than giving soft statements such as "it's better, more consistent, etc."</p>