Having skied both the Bone and E98 of these a bunch, I did find that both were pretty stout for my weight, both less than ideal. I don't know what the construction differences were between the E88 in 178 and the E98 in 180, but I found the former to rip under my feet, be super nimble, quick, easy to ski, powerful. One of the best all-around skis I have ever tried. The E98 in 180cm felt good in wide open crud and new snow, but a tank in short turns, less than ideal in bumps. Kevin loves it though in 188cm, he has 40lbs on me, he also likes the Bonafide, whereas I lean toward the softer E88 and Kabookie.
I would say the E98 is more technically oriented than the Bonafide. It feels more powerful at the top of the turn, a better carver, more powerful at speed, but yes, also more demanding. The Bonafide has a larger sweet spot, is more playful and soft-snow oriented. I think which one you like would depend on how you ski and what you like to feel in the turn, feedback (more or less).
The difference between skis like the E98 and the Bonefide on the one hand and skis like the E88 and the Kabookie on the other: the metal maybe? The E88 has none, I believe, nor does the Kabookie.
Also, in my experience, the stiffness of a ski is relative to its lenght. A longer ski of the same construction always seems more forgiving, flexible and pliable to me. I suppose metal sheets inside the ski only grow with it in one dimension (length), and not in thickness as well.