Currently, the most popular library for working with SVG is Raphaël. One of the primary reasons Raphaël became the de facto standard is that it supports browsers all the way back to IE 6. However, supporting so many browsers means only being able to implement a common subset of SVG features. Snap was written entirely from scratch by the author of Raphaël (Dmitry Baranovskiy), and is designed specifically for modern browsers (IE9 and up, Safari, Chrome, Firefox, and Opera). Targeting more modern browsers means that Snap can support features like masking, clipping, patterns, full gradients, groups, and more.
via Snap.svg – Why Snap.