What type of double stroller is the best? Side-by-side or Tandem?

I am looking at the side-by-side and a tandem stroller. Specifically, the Combi Twin Sport and the Contours Options Tandem Stroller. I have a toddler (almost 2) and am expecting a baby in December. I have heard that side-by-side are hard to fit through doorways, but tandems are very heavy.