We have a double jogging stroller that's side-by-side, and a regular stroller that's 'in-line', and we love both. The in-line model is nice for the mall, but we do have fights about who gets to sit up front.
The back seat is a little higher than the front, so the view is fine for both kids, and there's lots of storage room under the seats. My older two are 2 and 3 1/2, so they don't always want to ride. The stroller becomes the coat and baggage cart more than anything else!
The stroller fits through all doorways and elevators, but can be a little hard to turn. It's also a little harder to manage sun/rain protection - the canopies are smaller and don't cover as much.
Our side-by-side has individual seat recline and canopies, so both kids don't have to be in the same position - a big sell point for us. It's very easy to steer, turns on a dime and practically pushes itself (very well balanced) Storage is pretty good for a jogging stroller and I can easily see both kids as well as pass snacks and drinks without stopping.
One thing that we did - we took the kids to the stores with us to test drive a few strollers (Baby's R Us, Burlington Baby Depot, etc.) and see what 'felt' best for us. I wanted to make sure I could steer the darn thing and that everything would fit comfortably. Have you tried any models out, or do you have anything in particular you are looking at?