I would think a benefit of the side by side is they both can see everything and Parade watching is easier. The only thing that would be a hassle is shopping in the stores, I have trouble sometimes even with a single stroller.
If you have 2 adults going, then the best option would be to have 2 strollers...one for each of you. That would give the most maneuverability. And you could split up if one was sleeping and the other wasn't.