> Spine does class/inheritance closer to the "JavaScript" way [...]

Nope. See later on in this thread. Backbone uses constructor functions and prototypes, Spine uses Object.create. Both approaches have properties resolved correctly at runtime.

    > Spine seems to have given up the separation between Controller & View.

Nope. Spine Controllers == Backbone Views. Spine doesn't have an equivalent notion to Backbone Controllers (although if one were added, I'd imagine it would be called a Router).