The top one. Doesn't look much but seriously good sack. The two alloy staves can be formed to your back shape. I did that my walking for two days with 28kg load in it. Before that it was actually a bit uncomfortable.
These staves are fixed at a pivot point near the top and form a kind of shaped X shape The pivot allows for flex with your walk I think. It certainly seems to move with you rather than being completely stiff. It does transfer weight straight to your hips in a way I've never experienced in any other sack.
The other plus is the sideways V shape to the straps that link the hip belt and the back. The open part of the V is towards the back. This means the top part of the V pulls in higher up the back. The strap pulls tight on the other end. So fixed higher up through an open loop on the hip belt then back to the back with an adjustable webbing buckle that you pull forwards. It just works so well. I have no doubt I could climb with a bit of a load. I've certainly scrambled wearing it with 18kg load without any more difficulty than a light day pack load.
The hip belt is vertically very stiff. This load transfer. As I said I carried 28kg load in it and the sack was comfortable but the load weight I felt as I would on any sack. That load weight is high enough to know you're carrying it for sure.
The way I look at it this sack is like the crux ak 47 in many ways but with more volume due to its realistic 10 litres expansion. Makes it a good 60 litres not the stated 50 litres + 10 litres if you know what I mean. It's a simple, single chamber sack like the ak47 but it's lighter. Ahead of its time I reckon.
Sorry for my rambling about the best rucksack I've ever used. Colours date it I reckon. Very 1990s. Interestingly I saw a video of someone wearing what looked like the same sack. It was a guy filming the sledge his company sells. It's a campervan boot jump kit manufacturer (that's a campervan conversion system that allows you to remove the camping bit too use the van as a van during the week). Who makes a sledge that comes apart and is put together for use very easily.