I know a few very good multi-discipline folk who have opted for skis and only really bring their boards out for heavy powder surf days. They insist skis are just easier and more flexible.
I'll agree here. I don't even think of grabbing my snowboard on a hardpack day, and on big powder days skis have the advantage when the terrain flattens out. My rockered fat skis have as much or more surface area as my powder board, and I can't say I miss having to swim out of deep snow lying down on my board.
I like snowboarding simply because of how it feels. Skis might have as much flotation and more adaptability, but those factors only are a part of the equation. Snowboarding in deep pow gives me more of a feeling of euphoria for some reason. I don't understand why really, because I'm sliding on snow either way but facing sideways versus facing forward.