In reality there aren't many new functions. I've updated to the new iPhone every year for the last several releases. The iPhone 5 really gives you:
Honestly, the screen is much more than just bigger. The in cell display is gorgeous and vibrant.1. More screen space for reading text and seeing photos. It also helps with streaming video.
You do realise the YouTube app is available on the App Store? However, the mobile web app offers the same functionality anyway.5. One negative is the lack of YouTube app and Google Maps. While Apple has over 1500 people working on their maps app, it is no where close as good as Google Maps. This is one app I miss very much..