How much more powerful is it? I dont know, but you can find benchmarks on Google. Somewhere in the neighborhood of 8-10% if I remember right. Is it worth it for music production? Probably not. Exports and conversions *MIGHT* take slightly less time, but overall you won't notice much difference.
The 2.2 GHz i7 is plenty fast for tracking (32 in no problem), editing, mixing, MainStage. Honestly audio work isn't very CPU intensive. I have no problems working on my 2011 Mac Mini.