iPhone 4S is the fifth generation of iPhone developed by Apple Inc. The latest smartphone retains the exterior design of its predecessor, iPhone 4, but features some important upgrades compared to the previous model.

Perhaps, the most prominent features are Siri, a voice-recognition feature that allows users to control their phones by talking to them, cloud-sourced data and an improved 8-megapixel camera system. It also has a 3.5-inch TFT Retina multi-touch display and is loaded with the latest Apple operating system iOS 5.

However, it doesn't have some highly expected specs like edge-to-edge design, a larger display, 4G LTE and Near Field Communication (NFC) technology.

Meanwhile, Lumia 800 is Nokia's first mobile phone to run Windows Phone OS as a part of the first wave of Windows Phone devices to be released by the company. The latest smartphone from Nokia features a 3.7-inch AMOLED ClearBlack curved display blending seamlessly into the reduced body design and a 1.4 GHz processor.

Lumia 800 contains an instant-share camera experience based on leading Carl Zeiss optics, HD video playback, 16GB of internal user memory and 25GB of free SkyDrive storage for storing images and music. The latest Windows Phone OS-powered smartphone is expected to arrive in North America in early 2012.

Specs and Features Comparison

Lumia 800 weighs 142 grams and has a dimension of 116.5 x 61.2 x 12.1 mm while iPhone 4S comes with 115.2 x 58.6 x 9.3 mm and weighs 140 grams.

Nokia Lumia 800 displays 480 x 800 pixels at 252 PPI onto a 3.7-inch screen (slightly smaller than the Nokia N9 to accommodate the physical buttons) and the Apple iPhone 4S displays 640 x 960 pixels at 326 ppi density onto a 3.5-inch screen. However, Apple iPhone 4S appears to have the better resolution from these specifications.

Nokia Lumia 800 uses a 1.4 GHz single-core Snapdragon processor to drive Windows Phone 7.5 (Mango) while Apple iPhone 4S uses a dual-core 1 GHz A5 processor to drive iOS 5 and it is touted as being very simple to use.

Both phones have an 8-MP camera with autofocus and dual LED flash. However, iPhone 4S scores over Lumia 800 in video capabilities as it can take videos at 1080 pixels at 30 frames per second (fps) while Lumia 800 takes videos at 720 pixels at the same 30 fps.

For connectivity, Lumia 800 comes with support of HSDPA CAT 10 14.4 Mbps, HSUPA CAT 6 5.76 Mbps. On the other hand, Apple iPhone 4S has HSDPA 14.4 Mbps, HSUPA 5.8 Mbps support and also has CDMA EV-DO Rev. A (800, 1900 MHz) technology.

Apple iPhone 4S has fixed 16/32/64 GB internal storage while Lumia 800 comes only with 16GB internal memory and both phones lacks external memory slot.

Lumia 800 has a 1450 mAh BV-5JW Battery which is expected to give talk time of up to 13 hours and 9.5 hours on GSM and CDMA networks respectively. It gives a standby time of up to 265 hours and 335 hours on GSM and CDMA networks respectively. iPhone 4S has a Li-Po 1420 mAh battery with eight hours of talk time on 3G networks, up to 14 hours on 2G networks (GSM) and a standby time of 200 hours.

The estimated retail price for Nokia Lumia 800 will be about $595, excluding taxes and subsidies, while iPhone 4S costs $199 for the 16GB model, $299 for the 32GB model and $399 for the 64GB model under a two-year contract.