The Samsung Galaxy S2 smartphone is expected to launch in the U.S. in mid-July, following the HTC Thunderbolt, which was launched on March 17.

HTC's Thunderbolt is the first 4G LTE smartphone on the Verizon Wireless network. It is a CDMA variant of the HTC Desire HD. As of spring 2011, this phone is considered the flagship phone for Verizon, going head-to-head with the HTC EVO.

 

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But Samsung's Galaxy S2, which is expected to come in four versions in the U.S., was launched worldwide and recorded phenomenal global sales of 3 million units in 55 days in the U.K.

The Galaxy S2 is super-thin, measuring merely 8.5mm (0.33-inch) in thickness and weighs about 4 ounces. These specifications beat HTC Thunderbolt's vital statistics as the HTC smartphone weighs 6.23 ounces and is 14mm (0.56-inch) thick.

But the ThunderBolt runs on Verizon's 4G network, which can manage download speeds up to 12 Mbps, and upload speeds up to 5 Mbps. Its 4G coverage includes 45 cities, and 60 airports in the U.S. By the end of 2011, Verizon claims that the 4G service will extend to 100 more locations.

The ThunderBolt is the first phone on Verizon's network that uses a physical SIM card, versus MEID or ESN, for device authentication.

Below are the features of Samsung's Galaxy S2 in comparison with HTC Thunderbolt:

Operating systems: HTC Thunderbolt runs on Google Inc.’s Android 2.2 Froyo OS. On the other hand, Galaxy S2 runs on Android 2.3 Gingerbread which is the latest smartphone version of Android OS.

Though Froyo isn't quite as refined as Gingerbread, it has true multi-tasking support, Wi-Fi hotspot tethering and Adobe Flash support. But in Gingerbread, the user interface is refined, the soft keyboard and copy/paste features have been improved, and support for near field communication (NFC) has been added.

Camera: The Galaxy S2 has an 8MP single-LED flash camera with 1080p HD video recording at 30 frames per second and 2MP fixed front-facing camera for video chat. HTC Thunderbolt sports a rear-facing 8MP dual-LED flash camera with 720p HD video recording, and a front-facing camera has 1.3MP for video chat.

Screen: HTC Thunderbolt sports a 4.3-inch WVGA TFT screen with 800x480 screen resolution. Galaxy S 2 sports a 4.3-inch Super AMOLED screen with 800x480 screen resolution.

Processor: Galaxy S 2 is powered by a dual-core 1.2 GHz ARM Cortex-A9 Mali-400MP GPU Orion processor with 1GB RAM. Thunderbolt is powered by single-core 1GHz Qualcomm MSM8655 Snapdragon processor with 768MB RAM.

Size: The Galaxy S2 has a 125.3 x 66.1 x 8.5 mm and weighs 116 g, while Thunderbolt 4G is 122 x 66 x 13 mm and weighs 164 g.

Input: The input features found in HTC’s smartphone are: accelerometer sensor for UI auto-rotate, proximity sensor for auto turn-off, HTC Sense 2.0 UI and multi-touch. Galaxy S2 has features like TouchWiz UI version 4.0, multi-touch input, accelerometer sensor for UI auto-rotate, touch-sensitive controls, proximity sensor for auto turn-off, gyroscope sensor and Swype text input.

Storage: Galaxy S 2 boasts of 16/32 GB internal storage and via a microSD card slot it can expand up to 32 GB, while ThunderBolt comes with 8 GB internal memory and via a microSD card slot it can expand up to 32 GB.

3G: Samsung Galaxy S 2 has HSDPA 21 Mbps and HSUPA 5.76 Mbps support, while HTC’s smartphone has Verizon’s Rev. A up to 3.1 Mbps along with LTE.

WLAN/Bluetooth/ USB: The Wi-Fi 802.11 b/g/n DLNA is common in both the smartphones but the Galaxy S2 has an added Wi-Fi Direct feature. The Bluetooth version found in Thunderbolt is 2.1 with A2DP and EDR while Galaxy S2 has version 3.0+HS. Thunderbolt has microUSB version 2.0 and Galaxy S2 has version 2.0 microUSB (MHL).

Battery: With a battery capacity of Li-Ion 1650 mAh, Galaxy S2 leads when compared to HTC Thunderbolt’s Li-Ion 1400 mAh battery.

Pricing: The Galaxy S 2 is expected to be priced at $599 to $699 for unlocked 16GB version, while the locked version to be sold on contract from U.S. wireless carriers is expected to be in the $250 to $300+ price range. HTC Thunderbolt is priced at $569.99 on full retail price, while the locked version with 2-year Verizon contract is $249.99.

Other Features: The common features found in both the smartphones are SMS threaded view, MMS, Email, Push Email, IM, HTML browser, stereo FM radio with RDS, A-GPS support, digital compass, organizer, Google Search, Maps, Gmail, YouTube, Google Talk, Picasa integration, voice memo-dial-commands and predictive text input.

Also the other features found in the HTC Thunderbolt include video Skype, SNS integration, built-in kickstand, MP3/AAC+/WAV/WMA9 player, DivX/Xvid/MP4/H.263/H.264/WMV9/player and document viewer.

The Galaxy S2 has other features like RSS, Java via third party application, NFC support optional, TV-out via MHL A/V link, MP4/DivX/XviD/WMV/H.264/H.263 player, MP3/WAV/eAAC+/AC3/FLAC player, image and video editor and document editor (Word, Excel, PowerPoint, PDF). Samsung is planning to introduce the Samsung Hub, which will bring users over 2 million books, games from Gameloft and 12 million selections from 7 digital.

Reviews of the Galaxy S2 have been positive. Engadget gave the device a 9/10, calling it the best Android smartphone yet and possibly the best smartphone, period. CNET UK gave the device a favorable review of 4.5/5 and described it as one of the slimmest, lightest mobiles we've ever had the privilege to hold.