Rainer Brockerhoff examines the design of the Lightning connector and the advantages over micro-USB (via The Loop):
You can see that there are 8 pins and that the plug has a metallic tip which, from all accounts, serves as the neutral/return/ground. Since the plug is described as “reversible”, the same 8 pins are present on the other side and, internally to the shell, connected to the same wires. However inside the connector you can clearly see that the mating pins exists on one side only – presumably to reduce the internal height of the connector by a millimeter or two, at the expense of slightly better reliability and a doubled current capacity…
…People keep asking why Apple didn’t opt for the micro-USB connector. The answer is simple: that connector isn’t smart enough. It has only 5 pins: +5V, Ground, 2 digital data pins, and a sense pin, so most of the dock connector functions wouldn’t work – only charging and syncing would. Also, the pins are so small that no current plug/connector manufacturer allows the 2A needed for iPad charging.
Although there will be some issues with the transition, I am very positive about the new connector—the durability and smaller design will probably mean that there won’t be issues with the cable separately from the perpendicular Dock Connector. While I agree that micro-USB could be a good option in theory, the lack of flexibility and iPad charging are dealbreakers.