Support for 3G Networks

• As noted by its title, the iPhone 3G supports 3G wireless connections through AT&T. By connecting to a 3G network, the iPhone 3G featured higher connection speeds for telephone service and mobile Internet access. The original iPhone only had support for the now out-of-date EDGE standard, which was much slower.
  
  

Battery Life

• The iPhone 3G has a longer battery life than the original iPhone. However, the difference is not too major. The iPhone 3G battery will last for approximately 10 hours of talk time and 300 hours while on standby. However, the original iPhone's battery life was not too far under that amount, with 8 hours of talk time and 250 hours of standby time.
  
  

GPS

• The iPhone 3G was the first model to feature a global positioning system. Using the GPS, the iPhone 3G can pinpoint a user's exact location and even tag an exact location when taking photographs with the Camera app. This feature has remained standard on all later iPhone devices, but the original version did not support it.
  
  

Capacity

• While both the iPhone and iPhone 3G are available in 8 gigabyte and 16 gigabyte sizes, the original version also sold in a 4 GB version. However, Apple chose to stop manufacturing the smaller 4 GB iPhones when the iPhone 3G was introduced.
  
  

Cosmetic Changes

• A few cosmetic changes were made to the iPhone 3G. The original iPhone only shipped with a silver aluminum and black plastic back, while the iPhone 3G can be purchased with either a black or white back. Also, the headphone jack was recessed on the original iPhone, which caused problems with third-party headphones not fitting correctly. The iPhone 3G does not have a recessed headphone jack.