When the iPhone 4S and iPhone 4 are compared head to head, the iPhone 4S goes ahead with its Siri voice-activated personal assistant, A5 processor, CMDA+GSM chip, 1080p video capability, faster download speeds, improved graphics, improved camera and an intelligent switching antenna. The iPhone 4S also has a new operating system - iOS 5, as well, but that will be available for older iPhones as well.
In terms of design, iPhone 4 and iPhone 4S look identical as both have Glass Sandwich design. The letter S in the name iPhone 4S probably stands for improved 'speed'. The storage has also gone too high, up to 64 GB. The iPhone 4 storage went up to 32 GB only. The image quality is expected to be better even in low light conditions, the video resolution would also be better.
The iPhone 4S comes with an 8 megapixel camera compared to the 5 megapixel of iPhone 4. In terms of pixels, the front facing camera goes from 720 pixels to 1080 pixels though it still remains a 0.3 MP one. The iPhone 4S also has hybrid GSM/ CDMA cellular connectivity whereas the iPhone 4 had quad-band GSM/ CDMA cellular connectivity.
Simply stated, the iPhone 4S owners will find it easier to roam between countries which are predominantly GSM network country and those places where CDMA networks are prevalent. The faster A5 dual core processor will make it powerful device, with a claimed battery life of 8 hours. Last, but not the least is the Siri personal assistant which may prove to be quite an attraction for the users. The screen size in both the phones is 3.5 inches with 640x960 retina display.
About the RAM, a website has claimed it would be 1 GB for iPhone 4S but we didn't find supporting evidence on the Apple website. The iPhone 4 has a RAM of 512 MB only.