iPhone 4S hit the stores Friday last, after a long course of anticipation about iPhone 5.The new smartphone runs on Apple's new iOS 5, OS sporting some of the rumored features and specifications that turned cacophonous over the Internet in the past few months.

Though the smartphone looks the same as iPhone 4, its hardware includes an improved processor, a larger 64 GB capacity memory, alternating antennae, new chipset and an amazing personal assistant, Siri, which makes it's a strong contender in the smartphone market. Apple has sold more than 4 million units of the new iPhone within 3 days of its release.

The other smartphone which has hit remarkable sales is Samsung Galaxy S2, which was dubbed as the iPhone 5 Killer. Samsung has announced that the sales of Samsung Galaxy S2 have exceeded thirty million so far.

Galaxy S2 is powered by Android 2.3 Gingerbread OS and it comes with an 8-megapixel camera with flash and can record HD video in 1080p and a front-facing 2-megapixel camera for video chat. Galaxy S2 comes in three variants AT&T, T-Mobile and Sprint, all the versions will sport 4G treatment offering speed faster than iPhone 4.

Apple's iPhone 4S and Galaxy S2 are the two most talked about smartphones as they promise blazing performances. The two can be compared on the grounds of design, operating system, processor, camera, storage and battery.

Size: While Apple iPhone 4S comes with 115.2 x 58.6 x 9.3 mm and weighs 140 grams, Samsung Epic 4G Touch on Sprint comes with 129.5 x 68.6 x 9.6 mm dimension and weighs 129 grams, T-Mobile has 131 x 70 x 9 mm dimension and AT&T version will come with a 4.3-inch display, which will feature 125.3 x 66.1 x 8.5 mm and weighs 116 grams.

Display: The Sprint and T-Mobile versions of Galaxy S2 have 4.52-inch display screens, while AT&T has a 4.3-inch screen. Galaxy S2 Epic Touch 4G comes with 4.52-inch 480 x 800 pixels Super AMOLED Plus capacitive touchscreen display. The RGB matrix makes the smaller texts clear. The Super AMOLED Plus display increases readability and consumes less battery.

Camera: Both Samsung Galaxy S2 and iPhone 4S have a rear-facing 8-mp camera with LED flash and 1080p HD video capture capability. Galaxy S2 also has a 2-megapixel front-facing camera for video calling, while iPhone 4S has a VGA camera for video chat.

Processor: iPhone 4S has the same processor as iPad 2, A5 chipset powered by 1GHz dual-core ARM Cortex-A9 CPU, PowerVR SGX543MP2 GPU. The Sprint and AT&T variant of Samsung Galaxy S2 is powered by dual-core 1.2 GHz ARM Cortex-A9 Mali-400MP GPU Orion chipset, while the T-Mobile variant is powered by a 1.5 GHz dual-core Qualcomm APQ8060 processor.

Storage: For the first time Apple is marketing an iPhone with 64 GB. The smartphone comes with a fixed internal storage of 16/32/64GB, while Samsung Galaxy S2 supports 16/32 GB internal storage, which can be further expanded to 32 GB via microSD card slot.

Operating System: Galaxy S2 runs on Google's OS, Android 2.3 Gingerbread and iPhone 4S is powered by iOS5, Apple's new operating system which has more than 200 new features. However, most of the features in the iOS 5, including Notification System, Newsstand, widgets and reminder apps, cloud syncing are already existent in the Android platform.

Battery: iPhone 4S has a Li-Po 1420 mAh battery, with 8 hours of talk time on 3G networks and up to 14 hours on 2G networks (GSM). Samsung Epic Touch 4G has Li-Ion 1800 mAh battery support, offering more than 10 hours of talk time, while the AT&T version has Li-Ion 1650 mAh battery found in original Galaxy S2. The T-Mobile variant of Galaxy S2 has Li-Ion 1850 mAh battery support.

Near Field Communication: Apple iPhone 4S does not come with NFC capabilities (which is used to make mobile payment or serve as a keycard or ID card.) Samsung Galaxy S 2 supports NFC chip.