I was finally down to The Social Contract or Both Sides Now. I went with the later because I've seen it 5 or 6 times and it still makes me cry. The writing and the acting were spectacular on all sides.
If I could have voted for the best last quarter of an episode it would have been BSN. I swear, this is the first time I've cried over a TV show in, well, I can't remember when. I also loved Under My Skin, and finally decided that while it didn't have quite the impact of those last few minutes of the finale, I felt it had a slight edge in overall quality, so that's what I voted for. I hated to choose though.