Speed of development
EASY TO USE
Pre-tested modules and uniformity across modules (color, style, effect, feel)
A LOT OF TOOLS
Mobile-ready, and feel the same as the new Android L interface (Android L and Polymer were designed using the same UX principles of Material Interface)
Polymer is a library of ready-to-use, freely composable web components and standard polyfill scripts. It helps to build applications or web components.