At the time of release the iPhone 5 trailer clearly said that the LTE would be much faster compared to wifi. But yet I had not seen any sample. I had seen a video which showed a person testing the same with an application and showed up speed in mbps.
This was also provided in iPhone 4GB, but I never experienced the speed that assured. It shows that this iPhone has better enhancement. And does enabling LTE always will cause the network chip to perform lower.