Considering that the goal of the factory headers and the goal of these headers is completely different it would be foolish to say one is better than the other with a blanket statement. The reason why these eBay headers are so cheap is twofold, Chinese/Taiwanese labour is cheap (cents on a dollar for perspective) secondly another company spent lots of dollars researching the designs and these are copies. The design process for headers can get very complicated but their manufacturing process is very simple, that's why you can get the same design cheap.