Sidemount scuba diving is sweeping the world and becoming the configuration of choice for many in both recreational and technical diving.
Sidemounting your cylinders correctly provides a more streamlined profile making propulsion, buoyancy control and trim easier than backmounted configurations. Regardless of your orientation your center of gravity and buoyancy is always in the center of your body giving you greater balance and control.
Redundancy with two or more sidemounted cylinders provides additional safety in the event of an equipment failure and also the potential for greater gas reserves. While this is also the case for backmounted double configuration, sidemounting your cylinders means that your cylinder valves are in view and easily reachable in the event of an issue.
Managing each cylinder individually both in and out of the water means sidemount is easier for those with back or shoulder issues or who simply struggle with the weight of backmounted doubles.
For more check out this Blog article - 7 Reasons Why You Should Dive Sidemount.