why there are differences between G74SX-DH73-3D model?

. Standard specs as stated on Samsung's paper

- Data Link Protocol: Ethernet, Fast Ethernet, Gigabit Ethernet, IEEE 802.11b, IEEE 802.11g, IEEE 802.11n, Bluetooth 3.0
- Compliant Standards: IEEE 802.11b, IEEE 802.11g, IEEE 802.11n, Bluetooth 3.0


The links you mentioned are from system builders, meaning they can decide what to keep as standard and what to offer as part of system configurations for extra $$. It is normal business procedure, but can be confusing for consumers at time. Best thing is to print out all the configurations from the above vendors and then checking out the end price based on the same devices set-up.

Or if you prefer certain vendor from the above list, you can use the (standard) information to haggle

cheers ...

This is what this model standard is all about, from Samsung specifications advert as what it can support. This does NOT guarantee that you would get the same thing with different vendors. So do your homework and shop around. As mentioned above you can use this information as far as haggling a price or a configuration.

Specifications
General
System Type: Notebook
Built-in Devices: Stereo speakers, wireless LAN antenna, Bluetooth antenna
Width: 16.5 in
Depth: 12.8 in
Height: 2.4 in
Weight: 9.5 lbs
Color: Black
Bundled with: NVIDIA 3D Vision Kit

Processor
Processor: Intel Core i7 2670QM / 2.2 GHz
Multi-Core Technology: Quad-Core
64-bit Computing: Yes
Chipset Type: Mobile Intel HM65 Express

RAM
Installed Size: 12 GB / 16 GB (max)
Technology: DDR3 SDRAM
Form Factor: SO DIMM 204-pin

Storage Controller
Type: Serial ATA
Serial ATA Interface: Serial ATA-300

Storage
Hard Drive: 750 GB - Serial ATA-300 - 7200 rpm
Hard Drive (2nd): 750 GB - Serial ATA-300 - 7200 rpm

Optical Storage
Type: BD-Writer

Card Reader
Type: 8 in 1 card reader
Supported Flash Memory Cards: SD Memory Card, Memory Stick, Memory Stick PRO, MultiMediaCard, Memory Stick Duo, xD-Picture Card, miniSD, Memory Stick PRO Duo

Display
Display Type: 17.3" 3D Ready TFT
LCD Backlight Technology: LED backlight
Max Resolution: 1920 x 1080 ( Full HD )
Widescreen Display: Yes
Image Aspect Ratio: 16:9
Features: 3D Vision-Ready (120Hz), 30 Days Bright Dot Return

Video
Graphics Processor / Vendor: NVIDIA GeForce GTX 560M
Video Memory: 3 GB GDDR5 SDRAM

Audio
Audio Output: Sound card
Compliant Standards: EAX ADVANCED HD 5.0
Audio Input: Microphone

Notebook Camera
Camera Type: Integrated
Sensor Resolution: 2 Megapixel

Input Device(s)
Type: Mouse, keyboard, touchpad
Features: Built-in numeric keyboard

Networking
Networking: Network adapter
Wireless LAN Supported: Yes
Data Link Protocol: Ethernet, Fast Ethernet, Gigabit Ethernet, IEEE 802.11b, IEEE 802.11g, IEEE 802.11n, Bluetooth 3.0
Compliant Standards: IEEE 802.11b, IEEE 802.11g, IEEE 802.11n, Bluetooth 3.0

Expansion / Connectivity
Expansion Slot(s): 4 memory - SO DIMM 204-pin
Interfaces: 1 x headphones - output - mini-phone 3.5 mm ¦ 1 x microphone - input - mini-phone 3.5 mm ¦ 1 x SuperSpeed USB 3.0 - 9 pin USB Type A ¦ 3 x Hi-Speed USB - 4 pin USB Type A ¦ 1 x network - Ethernet 10Base-T/100Base-TX/1000Base-T - RJ-45 ¦ 1 x audio / video - HDMI - 19 pin HDMI Type A ¦ 1 x display / video - VGA - 15 pin HD D-Sub (HD-15)

Miscellaneous
Included Accessories: Carrying case, optical mouse
Features: Security lock slot (cable lock sold separately)

Power
Power Device: External
Voltage Required: AC 120/230 V ( 50/60 Hz )
Power Provided: 150 Watt
Output Voltage: 19 V
Output Current: 6.3 A

Battery
Technology: 8-cell
Installed Qty: 1

cheers ...