The LG Optimus G features a 4.7 inch display, 32GB of onboard storage which can be expanded through microSD, a 13 megapixel camera capable of 1080p HD video capture, a secondary camera for video calls and is powered by a quad-core processor and 2GB of RAM. Meanwhile the Samsung Galaxy S III features a 4.8 inch Super AMOLED HD display, 8 megapixel intelligent camera in the rear which is capable of 1080p HD video capture, a secondary front facing camera which is capable of 720p HD video capture, up to 64GB of internal storage which can be expanded through microSD, NFC connectivity, Wi-Fi, Bluetooth 4.0 and is powered by a quad core processor.
Check out the following video comparison between the LG Optimus G and the Samsung Galaxy S III
You can read the detailed comparison of the LG Optimus G and the Samsung Galaxy S III on PhoneArena