Optimus Black is sleek, slim and light weighing only 109g and only 9.2mm thick. The design is pure and simple with nice finish on the exterior and holds nicely in the hands. Xperia Arc is a step ahead with a design that is more stylish and catchy and even slimmer than Optimus Black with only 8.7mm of thickness and weighing just 117g. Xperia Arc has a clear advantage when it comes to a better design and looks.
Optimus Black has the latest 4.0 inch IPS LCD capacitive touchscreen with resolution of 480 x 800 pixels, and 16M color support. The display is extremely bright, clear and most readable compared to the other LCD panels around. Xperia Arc has 4.2 inch LED-backlit LCD, capacitive touchscreen with a resolution of 480 x 854 pixels and 16M color support and mobile Bravia engine. Overall both smart phones have excellent display but Optimus black has a slight advantage.
The major difference between the two phones is the camera resolution with Xperia Arc having 8.1MP with touch focus, geo-tagging, image stabilization and face and smile detection features. Optimus Black has 5MP camera with geo tagging and face and smile detection features. Both smart phones are able to record HD 720p video at 30 fps.
Processor and OS:
Both smart phones have processing power of 1Ghz. Optimus black has android 2.2 which can be upgraded to Android 2.3, and Arc already has the latest Android 2.3
Arc has 320MB of internal storage compared to 2GB in Optimus black; both smart phones have 512MB of RAM and memory card support up to 32GB. Optimus black has the clear edge again.