Friendly Sims have more success at cheering up Sims who are angry or upset. The same goes for Good Sims.
Friendly Sims often gain wishes to introduce themselves to new townies in the neighbourhood.
Pairing the Charismatic trait with the Friendly trait will allow Sims to build up relationships at a very fast rate, making them a powerful combination for making friendships.
Unlike Good Sims who cannot initiate fights at all, Friendly Sims can still be made to use all "Fight!" interactions. Because of this, Friendly Sims are still able to fight off burglars if they also have the Brave trait and/or the Can Apprehend Burglar hidden trait.