title: Doctrine: ORM QueryBuilder or DBAL QueryBuilder
body: <p>DBAL Query Builder:
  <a href="http://www.doctrine-project.org/api/dbal/2.3/class-Doctrine.DBAL.Query.QueryBuilder.html" rel="nofollow">http://www.doctrine-project.org/api/dbal/2.3/class-Doctrine.DBAL.Query.QueryBuilder.html</a></p>
  
  <p>ORM Query Builder:
  <a href="http://www.doctrine-project.org/api/orm/2.3/class-Doctrine.ORM.QueryBuilder.html" rel="nofollow">http://www.doctrine-project.org/api/orm/2.3/class-Doctrine.ORM.QueryBuilder.html</a></p>
  
  <p>Inside Doctrine there is 2 QueryBuilder that are quite similar, the DBAL one and the ORM one.</p>
  
  <p>What is the difference between those 2? Is there a big overhead using the ORM queryBuilder compared to the DBAL one ?</p>
  
  <p>(native query are out of question as I need to use dynamic where statement)</p>