Examples of how one or the other style didn't work usually come down to one thing and one thing only; poor shot placement. They both work well. The preference for me is purely a comfort thing. I'm really a freak about keeping blades scary sharp and I don't like those blades waving around out in the open. I feel safer using expandables. Problem is that AK doesn't allow expandables on any of our larger critters so I have arrows rigged with both; expandables for deer, caribou and black bear/ fixed blades for goat, moose and brown bear.