I think it depends on the situation, and I’ve seen both.
I’ve been in true partnership situations where we’ve had complete faith in each other’s abilities, and each contributes without egos being involved at all. When this has happened, it’s been fantastic.
More often than not, though, there’s a leader. Sometimes it’s a good leader who relies on his or her team and who serves as a unifier and visionary. Sometimes it’s an incompetent nitwit who gets in the way, micromanages and ensures failure. All too often, it’s the latter.
Personally, I dislike hierarchies, and I tend to rebel against them. The Peter Principle of people rising to their levels of incompetence often places incompetent, butt kissers with high EQs and no real abilities in charge.
For what it’s worth, I hate group brainstorming sessions far more than I dislike hierarchies. They almost always result in half-baked, lowest-common-denominator solutions where the loudest, least thoughtful and most aggressive person dominates. I’ve found that in reality, it’s typically the quiet, introspective, introverted and thoughtful people who say the least that somehow come up with the best solutions.