What it boils down too...........
Choose one and go blow some leaves. All 3 are powerful and all 3 will get the job done as fast as possible. We have a BR600 and 8500 and the 8500 stays home all year until the leaves start falling. It is far more powerful than the BR600 but the BR600 is lighter so we use it during the summer.
2013 Gravely 460Z 29EFI
2011 Gravely 36GR
2008 Gravely 160Z
2004 Gravely 34Z
1998 Lazer Z HP 48 (old faithful)