Speaking of neither, but trying to be helpful: check out KnockoutJS. Just used it for a fairly complicated project for a client. Goddamned delightful. Perfect (read: not dogmatic) separation between markup and code. CoffeeScript + Jade templating + KnockoutJS = web app delight.
EDIT: Backbone/Spine target different use cases than KnockoutJS, but KnockoutJS seems to target the more relevant ones.
EDIT: Backbone/Spine target different use cases than KnockoutJS, but KnockoutJS seems to target the more relevant ones.