The use of branch fittings instead of conventional fittings (buttweld tee, reinforcing pads and saddles) has the following advantages (example Weldolet):
Just 2 welds are needed, instead of 3 (less work and weld inspections)
Accelerated installation time
Less space is required, making the piping system design more flexible
The flow is fully unrestricted, due to the funnel design