When to decide King or Queen side castling? How do you decide to castle on king side or on queen side? i know king side is castling is the quicker than queen side with just 4 steps.

Does queen side castling favours more on attack, than compared to king side (defense)??
If pawns are more advanced on one side, or there is a material inequality to one side of your opponents pieces, castle opposite the majority of attack.  

Typically, king side becomes favored, probably in part because of the property of castling you noted:  that it's quicker to king side castle.  Well, that and the King isn't as close to the center with King
 side castling.  

Queen side castling is a bit easier to attack from however due to the imabalance of position (ie typically the other king is castled on its' king side).