One question I get a lot from our followers is whether side by side or tandem double strollers are better, and I gotta tell you, that's a really really hard call. The two biggest pros of a side by side, in my opinion, are not having to stop walking in order to get snacks or bottles to both of your children (since they're both within your reach) and hoisting the stroller over curbs is also easier.
I was nervous that a tandem would feel easy to tip and hard to maneuver around corners, but I gotta say the StrollAir Tango is neither of these things. The large wheels and wide back wheel base are very helpful with these issues. Also due to the large wheels, it has no trouble rolling smoothly over the biggest divots, that our double umbrella stroller was constantly getting stuck on! If pushing on slanted sidewalk, you have to use a bit more muscle to keep it straight than a side by side, but it performed light years beyond the Joovy Big Caboose we used 2 years ago in terms of stability and ease of steering and turning corners.
In some tandem configurations you could face the problem of one child kicking the other one, but recently we've had the issue in our side by side of our girls fighting, pulling hair, etc, so there's really no way to avoid this - if your kids want to fight, they will find a way, no matter what kind of stroller they're in! That said, in the StrollAir Tango you can have your children facing opposite directions - so YAY, I have found a solution!!
I've also found this tandem easier to get through the grocery store aisles. When my girls are next to each other in a wide SBS, they both stretch out their arms and legs (my twin "octopus") and grab or knock stuff of the shelf. SO frustrating. We've never found a main doorway our SBS couldn't get through, but it couldn't get through our bedroom doorway or the grocery store checkout lanes, which the tandem can. it's amazing what just a few inches in width can mean (the back wheels are the widest part of the Tango, about 25.5" wide. Our side by side is 29" wide and many are up to 32" or so!!)!
Very long story short, I don't think there's an easy answer as to side by side or tandem being better, you need to take both types for a test drive to see which will suit you better. Either way, StrollAir has got an amazing stroller for you. If leaning toward a tandem, I can't recommend their Solo to Tango highly enough! And if going for a side by side, their new TwinWay (pretty much a vamped up MyDuo) is the way to go!! Side note, their ReVu also sounds amazing - it's an umbrella stroller with a reversible seat!!