I'd also be happy at any of these - they're really all top notch, IMHO. If you golf at all, Grand Vista wins, with golf onsite. If you want water activities, fishing or small boat rentals, Cypress Harbour offers this. We love to walk around a resort in the evening. For that, Vistana Villages is lovely and romantic, with good paths near the water and waterfall. They are all located fairly near one another, with lots of restaurants within a couple miles drive. So you wouldn't regret a choice to stay at any of these.
I suppose a deciding factor for us would be the room size.
Grand Vista has some studio units and these are really just nice hotel rooms. So we'd only take a 1BR or larger at Grand Vista.
Vistana Villages has some smaller 1BRs without jacuzzi tub or balcony. So we'd only take a 2BR at Vistana Villages.
Cypress Harbour is all 2BRs, but some are a bit further from the lake, pools and activities. So if you go here, call the resort a week before and request a room with a lake view and you'll be closer to everything else too.
HTH! Enjoy!