I'll take a stab. As I understand it, these are the things that are hard to get at 7 months for each resort:
BWV: Standard view rooms and Grand Villas
BCV: Any room, esp studios (it's a very small resort)
VWL: Any room, esp studios (see above)
OKW: Grand Villas (the lowest point cost of any Grand Villa)
AKL: Value rooms and club level
SSR: Grand Villas and Treehouses
BLT: Any room, esp studios (it's the only monorail
DVC resort until VGF opens)
VGF: Any room
At all the resorts studios sell out before 1 bedrooms because they hold the same number of people but cost roughly half as much. Grand Villas go quickly because there are so few of them.
I get the impression that the following is a rough guide to what sells out first in general (though there will be many instances where this won't hold for one reason or another):
Grand Villas
Studios
2 Bedrooms
1 Bedroom
The result is that if you are looking at a 1 or 2 bedroom, you have a higher chance of finding something at another resort at 7 months. If you want/need a value or standard view studio, you need the luck o' the Irish. And if you are going to want a Grand Villa at a specific resort, you had better own there.