The Ions I used from last year (2010-2011 model year) were not stiff boots at all. I'd say that had a moderate amount of lateral stiffness (flexing nose to tail on your board) but absolutely no tongue stiffness, I could fold the thing in half with one hand. If you're looking for a high performance big mountain boot, those are not the ones. For reference, they're much, much softer than Salomon malamutes, Flow Rifts, and DC judge's.
I can't be much help on the Nike options, but they all felt pretty darn soft in the store as well.