If your Xbox 360 is not modded:
Yes, but with caveats. Most features, like items and mobs, will carry over. However, terrain-based features, such as the new Jungle Biome, will only generate in of an existing world. If you want to experience all of TU12’s new world generation, you should start a new world. minecraft xbox 360 title update 12 download better
Players could finally explore dense jungles, climb vines, and harvest cocoa beans. If your Xbox 360 is not modded: Yes, but with caveats
Here is a review of that specific update and its impact on the game. but with caveats. Most features
It seems you are looking for information regarding for Minecraft: Xbox 360 Edition, specifically regarding the download and why it is often considered "better" or significant.