Would love people's thoughts on the pros and cons of tandem versus side by side double strollers.

My friend has twins and she purchased a tandem stroller. I would also prefer using a tandem stroller because it takes less space than a side by side double stroller. If you're in a crowded mall or entering an elevator, it's easier to push a tandem stroller as it takes up the width of one person than two (for a side by side stroller). With a tandem stroller, it's also easier to navigate aisles as compared to a side by side stroller.