They are very different packs, IMO. Fit and feel is not similar. I don't have the new kifaru frame. But have the original exo, the K2, orginal duplex frame and hunter frame.
Hunter barreled and hurt my lower back (sold)
duplex frame if not packed well i got lower back pain with the adjustment strap metal tabs. (new frame fixes this)
oringal exo with super heavy loads twists with you a lot. its ok, just know if you got a heavy load and are hiking over dead falls it will twist on you
k2 is more stout and doesn't twist.
i don't see any pack giving you a good breathability back. If you are hiking and sweating there won't be enough air flow to dry off your back. They all get hot and my back shirt is always soaked (wool).