I would go with the gravely with the efi for sure. The kohler efi is absolutely a smooth low fuel usage sweet running engine. I have the 29efi on my gravely 460. That 260 is much beefier machine than that tiger cat. Don't worry about getting parts for the gravely. If the dealer doesn't have a part they can overnight it. I don't cut your type of grass but like Retrodog above said I have heard great things about the xfactor II in southern turf. I know up here scags dont leave a super fine smooth manicured cut quality so I would never consider one for my area even thought a lot of guys use them here. I always watch these guys and scratch my head wondering why they use scags with the slightly shaggy looking cut they leave behind.
2013 Gravely 460Z 29EFI
2011 Gravely 36GR
2008 Gravely 160Z
2004 Gravely 34Z
1998 Lazer Z HP 48 (old faithful)