As to the fuel efficiency of the 570 vs the 580 its tough to say. The tank is smaller and I believe the rpm's are higher on the 570 so I'm not sure about that. As to louder, the decibals are 110 for the 580 vs 112 for the 580. Its nice to have both but with the exception of comfort I'd never give up the 580 for the 570.
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