I’ve had a lot of packs, but haven’t had a KYSS pack. I do have a FAS pack and like it so far, because of its smaller size and pocket configurations. It is very very similar in size to the Eberlestock Bandit, which I also have. If you’re looking for something more budget friendly, the Bandit ia a great choice.
I one-stick climb. The Bandit and FAS both carry a one-stick, but the FAS does it better with the compression straps. Adding straps to the Bandit makes it carry well too.
The small size and pocket organization, along with the ability to customize with exterior pockets make the FAS the better choice for me. Although, I found that I only really needed just two small molle pouches, and only for occasional quick-grab things.
Semper Fi,
Mike