Well, my Retina MacBook Pro is actually also "better" than my old MacBook Pro (2011 model) in that regard, so I don't think it's the difference in "power", but more of engineering.
Keeping my fingers crossed that my iPhone 5 will be the same. It's painful going back to the iPhone 4 after listening to the rMBP, really.
It's also to note that the MBP 2011 model sounded the same as my iPhone 4/4S (I have both and use them interchangeably), so...
Edited by Bill-P - 9/21/12 at 9:07am