I just bought a Husqy 570BTS and it is an amazing machine.
I went with the 570 over the 580 for the increased MPH for scouring power.
The 560 is not as powerful as the 570, the 560 is: 232 mph/632 cfm air speed
The 570 is 236mph and 770 CFM.
IMO, the 570 is worth the few extra $ for the extra 100 CFM which is what helps you blow the huge windrolls of leaves.
I also like the larger/improved air filter that should help it last a long long time.
I avoided the Stihl due to its 4 stroke type engine that will, at some point, require the valves to be adjusted - possibly more than once over the lifetime of the unit.