The Ultegra CN-6800 11-speed chain is 14 grams lighter and 20% more durable than the CN-6701. The CN-6800 is 5.62mm wide - slightly more narrow than the 5.88mm 6701 chain. One nice feature is the 11-speed chain is symmetrical so there is no need to worry amount putting it on in the correct orientation - it can be put on in either direction.
One of the key features of the CN-6800 chain is the PTFE coating that contributes to a claimed 20% increase in durability. The PTFE coating also provides a smoother feel during shifts and less drivetrain noise even when cross-chaining. Chain pins for installation are included with the chain.