From what I remember, a primary reason Lodash was created as a fork of underscore was to address the "solution" that fastjs provides - underscore had problems with edge cases like sparse arrays, so lodash was created as a spec-compliant alternative. http://stackoverflow.com/a/13898916/1869609

Only in marketing buzz, and only if he cares.

lodash is as fast as fast: see the JSPerf results posted elsewhere. John manages lodash well. He has managed it well for quite a while. Why switch to another library with no track record for little or no gain?