Don't let the flex fool you, the Kaiju can easily handle any free riding you throw at it. Vermont, Maine, Utah, Colorado, pipe, park, steeps. I don't know about bigger terrain like AK etc but Nicolas Muller rides them all over the world. However if you "prefer" the feel of a stiffer boot the Ion is a click or two stiffer. But I find my Kaiju do everything just as well as my Ions and leave me feeling a little more mobile and unrestricted in my movements.