Longer runs demand more hydration. The Kalenji hydration backpack holds 1,5 liters of fluid. That is more than twice the Nathan Quickdraw Plus can hold.
The front pockets hold enough gels for my marathon needs.
In the main compartment I put my phone and ID card behind a zipper pocket. The blatter is hung in the main compartment. I have shortened the tube to stop it from bouncing in my face.
Running with the backpack is comfortable. The pack sits high up on your back and moves with your body.
My marathons take 4 hours. Not sure if I would take the backpack on shorter/faster runs as it adds extra weight (mostly the fluid)