Apart from the design difference - the biggest difference is AirPods are wireless while EarPods are not wireless. The AirPods comes with lot more openings compared to EarPods.
Yes, many people does that to improve the battery life.While using only one AirPod at a time, your iPhone will switch over to a mono mixdown so, you can hear both sides of any stereo.
Yes, Apple Airpods are compatible with Macbooks.
Yes, you can connect Airpods with iPhone 6.
Look past their offbeat design and you'll find that Apple AirPods' compact size and high convenience factor are a winning combination.