Tandem strollers and side-by-side strollers each have their strengths and weakness inherent in their design. Parents love or hate them depending on how well the strollers fit into their lifestyle.
Tandem double strollers are longer but narrower and are better for navigating narrow aisles and crowded walkways. However, the lengthier design results in a wider turning radius that makes it difficult to make corners, causing it to be somewhat unwieldy in trying to move around obstacles.
The side-by-side design, is shorter but wider, the exact opposite of the tandem double stroller. It is easier to turn at bends but it becomes problematic when walkways are too narrow to accommodate its width.
Parents have reported that some stores do not have entrances wide enough to allow side-by-side double strollers through and they often have to be referred to enter from the back of the store. Depending on conditions at your local department store (or where you normally do your shopping), you should get a double stroller that best fits your needs. A tandem double stroller for a busy supermarket with narrow aisles; or a side-by-side double stroller for bendy lanes with wide corridors.
Tandem double strollers require the children to sit one behind the other, and more often than not, children fight over who gets to sit in front. The child behind doesn't get much of a view and trips to the mall can get boring for the child quickly. A disgruntled child is a much bigger headache than ferrying your children around the mall. But of course, not all children fight to sit in front, some children gladly sit at the back where they feel more secure and shrouded. On the other hand, placing two chatty children in a side by side double stroller can be another form of headache, especially when they start screaming at each other.
Another problem with tandem double strollers is the fact that the stroller does not recline fully because there is another seat behind the first one. Side-by-side double strollers do not have this problem and both seats are able to recline fully for babies or children to sleep in. However, experienced parents will tell you that the reclining feature is not necessary for children to fall asleep in the double stroller. Children will fall asleep anywhere, in any position, when they do.
Depending on the type of environment you live in, different stroller design will be suitable for you. So before you actually buy your double stroller, have a long hard think about the places you visit and the places you are likely to bring your babies along. Don't idealise walks with your babies as leisurely strolls in the park. Think about real situations; busy malls, narrow pavements; those are the real challenges you will face and thinking through them will help you decide which double stroller will suit you better. There is no perfect double stroller, but the least you can do is get one that is most helpful to you.