I just use SMS every time. It's not a negotiation that goes back and forth. They know clearly what has gone wrong by now and someone just needs to say it.
Face to face meetings for the 'warnings' and the 'talks'. Then you go home, think it over, and decide whether to pull the trigger.
It's bad to sit and meet face to face just for the sole purpose of saying that it's not working out. Very often, one of the problems is a lack of communication so meeting is difficult in the first place.
I think a lot more people should break up. But instead they can't say it because meeting makes it too difficult.
One of my uncles was divorced through SMS. One of my friends didn't even get a break up notice. She called her boyfriend after the guy didn't contact her for months. Then that guy's wife picked up. Yup, that guy got married without even breaking up with his earlier girlfriend!