Unity and XNA are very different. XNA is a very basic library to roll your own game engine. Unity is a game engine that handles scenes, game objects, physics,

Unity and XNA are very different. XNA is a very basic library to roll your own game engine. Unity is a game engine that handles scenes, game objects, physics, animations, complex 3d animations and very sophisticated graphics effects all blended together in a powerful IDE. XNA is a hammer and nails, Unity is a house.