The internal frame backpack is the pack for hikers. With an internal pack the center of gravity is better when going up hill. The internal frame system has a larger main compartment and fits closer to your body. It has fewer places to strap items to the outside, that way, if you go thru a tight place you won’t snag up on something.
The load lifters can be adjusted to shift the weight, back and forth off your shoulders and hips. Just the slightest adjustment can help in rough terrains. It really helps to move the weight off your shoulders, after a real hard climb up hill. The internal frame backpack can be easier on the back with proper padding and support.