I normally use a size small Aura 65 pack. The frame on the size small Ariel 65 is at least two inches longer than on the Aura, and made a noticeable difference in comfort when using it on a 7 day 70 mile trip. I have heard that this pack is meant to sit lower on the hips. I am used to being able to sit my pack closer to the waist above the hip bone to relieve pressure on the shoulders, but this was impossible with the Ariel. I experienced a lot of hip pain while using it. The lack of external pockets in comparison to the Aura model means that everything has to go inside the main compartment, which makes it more difficult to access things you want every day without unpacking the whole bag.
Salt Lake City, Utah