Battle of the Bedding: Duvets vs. Comforters

Duvet cover plus insert versus comforter? It's a debate as old as time (or at least, as old as duvets and/or comforters.) Chances are, whichever side you happen to reside on, you're pretty darn adamant about it being the right side. We're playing Switzerland here (even though we certainly have our own opinions...that are obviously correct), and looking at the pros and cons of each bedding option.