The bigger iPhone 5 display screen is certainly advantageous and looks appealing in the leaked photos. But in my opinion the popularity of the new iphone also depends a lot on the new iOS 6. We can easily get an android or windows phone device with a similar or larger screen size but you cant get iOS on any other device ?.
Lastly will buy it because it has the best touch ever. No lags at all, again iOS plays an important part here.