HellsCanyon
WKR
Some terrain simply demands stiff, heavy boots, but frankly I think a lot of guys (myself included) use too much boot for the conditions. I tend to err on the side of too much rather than not enough.
I know there are some guys on here that log WAY more miles than myself, but I log a couple hundred every year with a good percentage of those being off trail and in some very rugged conditions and have included some very heavy packs and don't think I've wished for stiffer boots once. I'm sure with some mountaineering type stuff you may want them, but I've hiked a lot of cliffs and steep nasty terrain. Guess it just comes down to personal preference and what your legs/ankles/feet require.
Mike