I like stiff boots because I like to carve as hard as possible (when there's not fresh snow it's my favorite thing to do) and for that purpose an ultra stiff, resposive boot and binding combo helps you feel everything and make split second adjustments while charging.
Think of it like a cars suspension. For racing you want super low, super stiff suspension with tires that have very stiff sidewalls. For all around driving you want something in the middle.
I'd go with casuals advice, buy something in the mid-range that fits you really well. Although I find for me boots do pack out a little bit... I have to buy them a little too snug and then wear them around the house for a day before hitting the snow with them.