AKV is a pretty large resort, and if I had to flip a coin I'd guess that you'll have a better chance of getting in to AKV at 7 months than you will at BLT (especially for Christmas).
Obviously don't have any data to support this as BLT is so new, but just my gut assumptions.
If you're even considering SSR you should be looking at resale instead of buying SSR direct as you can save a TON of cash (SSR is around $91 direct with the current incentives and closer to $70 resale).
MFs at BLT are much lower at than AKV making BLT a much more "cost effective" place ot own over time.
HOWEVER - keep in mind that your points won't go as far at BLT as they will at AKV - this is the case regardless of where you own so it shouldn't really factor into your choice around AKV vs BLT as a home resort.
For example, a 1BR Savanah view at AKV in the "premier" season is 345 points, with the concierge view being 402. A lake view at BLT for the same period is 386, while the MK view is 466.
Again, the last paragraph shouldn't factor in "where" you own, but just something to keep in mind.
Good luck on your choice,
Chris