External frame packs and internal frame packs differences:
External
External frame packs are designed to carry large loads for long distances typically over well established trails without a lot of low overhanging branches or narrow passages.
Benefits of external frames:
- Proper loading is accomplished more easily while also carring awkard, unbalanced loads easily.
- More weight can be carried comfortably while allowing the wearer to walk erect.
- Allow for increased ventilation, thereby allowing you to remain cooler.
examples of external frame backpacks – HERE
Internal
An internal frame pack is ideally suited for trips where balance is critical or for people who carry loads while doing activities that require independent arm movement (skiing, climbing, hiking on rough trails, etc.).
Benefits of internal frames:
- Flexible suspension that can be formed to follow the contours of the spine.
- Load rides close to the back and brings the packs center of gravity closer to the wearers’ center of gravity, creating a balanced and stable load during higher speed activities.
examples of internal frame backpacks – HERE
Info Sources:
https://www.kelty.com/news.aspx?NewsTypeID=10&showarticle=90
Backpacking packs come in two types. External frames packs are those with a framework on the outside. These old-school-style packs are the best choice if you’ll be hiking mostly on groomed trails carrying lots of weight. They’re especially good at transferring the load so you can hike in a more comfortable upright stance. They’re also about half the cost of an internal frame pack, which has its support hidden inside like a skeleton.
Internal frame packs are usually more form-fitting, so they are better for guys who’ll be hiking rugged trails that require freedom of movement and balance. Most internal frame packs have one huge compartment with a couple of zippered access points, whereas external frame packs usually have lots of smaller compartments that make organization easier. You can also easily attach extra gear – such as a sleeping bag or fishing rod – to the frame.
Info Source:
https://boyslife.org/outdoors/askgearguy/3239/internal-or-external-frame-on-backpack/
The benefits of external frames are thus: They position the weight high on your back, allowing good vertical load transfer to the hips and a more upright walking posture. (With an internal frame, have you ever found yourself leaning forward while you hike to counterbalance the load on your back? You don’t have to do that with externals.) They also work great in hot weather, because the frame keeps the pack suspended away from your back, allowing lots of airflow between you and your pack. And, they tend to be very affordable.
The downsides to externals are that, because they carry the weight high and away from your back, they don’t have the best stability. So, you run the risk of feeling tippy and off- balance during scrambling maneuvers or when climbing or descending dicey terrain. The packbags also tent to be big and square-ish (not compact and streamlined like internals), so if you find yourself in a bushwhacking situation, you’ll likely get hung up on branches and brush. For those reasons, externals are best suited for hiking on established trails.
Info Source:
https://www.backpacker.com/gear/ask_kristin/335
Additional Backpack options can be found HERE