The December Adventure season is one of the hardest times to book DVC without calling at the 11 month window. Of course, a lot depends on what resorts you are looking at.
None of the resorts are all that difficult to get if you use your home booking advantage. If you wait until less than 7 months out, then everyone can reserve at any resort so a lot more challenging to get what you want.
Which resort(s) are you considering? If it's SSR or AKV, you won't have a problem if you book at 11 months .
If you want concierge level accommodations at the AKV, VWL or SV/BW view at the BWV, a 2 bedroom with 2 queen beds in the 2nd bedroom at the BCV or a Grand Villa anywhere, you may have to call day by day to get a reservation between Thanksgiving and New Year's Day. But you will almost surely get it if you do.
As Granny said, it's a whole 'nother story if you have to use the 7 month window. Buy where you won't mind staying if you can't change at 7 months. If you can't book more than 7 months in advance, it doesn't matter where you buy.