Advantages and Disadvantages of Internal Frame Backpacks
I hear people talking all the time about external frame backpacks or internal frame backpacks. Asking which is better, which is lighter, etc? Well if you ask me, it's more about comfort, weight and personal preference.
Is one model better than the other? That depends on what and where you will be hiking.
In Boy Scouts, I didn't see many internal frame backpacks until the 1990's and they are becoming more popular every year. We would start the boys (usually around 10 1/2 – 11 years old) out in external frame backpacks and when they got older they usually bought the internal frame models.
The Scouts would give me various reasons for going to them:
More compact, therefore more stable
Better packing and easier to get to items
Better manageability on the trail allows you to move easier on the trail
More pockets which allows for better packing and organization
Better comfort, hugs the body better for hilly and mountainous regions
Additional external pouches can be attached for expandability
They can be adjusted for a better fit to the hiker. That's not to say that the external frame cannot be adjusted to a good comfortable fit. It really means that the internal is a snugger fit and therefore a better fit.
The frame is built into the backpack. Therefore, since it is one unit, the backpack will fit and move as one unit with the hiker. Giving you more balance and motion control.
The only real negative to the internal frame is that they cost a bit more than external frame backpacks. And, it's up to you if you want to start a child with one.