What's the difference in baking bread in a loaf pan vs. in a Dutch oven?
There's two important distinctions:


The dutch oven is preheated, so the oven conveys a lot of heat, rather quickly.  This causes some steam to be pretty much immediately made.
The dutch oven is covered.  This traps the steam previously made.  This is trying to replicate steam injection and the goal of most methods that cover the loaf.


Steam keeps the crust from hardening and promotes better oven spring and crisper crust.  The steam basically allows the bread to 'swell' more in the oven.  Steam also gelatinizes the starches in the crust and formes a better 'shine' and 'crisp' on the finished product.  The dutch oven is then uncovered after awhile and the crust hardens.