What is the difference between Android 4.4W (API20) and Android L (API20, L Preview) in the SDK Manager?
L Developer Preview is the preview of Android 5.0
Android 4.4W is Android Wear SDK
Android 4.4W Target Android Watches
See Image: http://i.stack.imgur.com/ztzXa.jpg
while Android L (API20, L Preview) is the preview of the upcoming release of Android. It is subject to change and it's stability is not guaranteed