Buying direct or resale isn't really going to change your ability to book
DVC at the 7 month window.
The more owners there are, the harder it is going to be to trade to some of the resorts at 7 months. Depending on when you travel, you may or may not find exactly what you want.
For example, the fall is very busy for DVC, so trading out to places like BWV, BCV, and BLT can be difficult with Food & Wine and the holiday parties at MK. Nothing is ever impossible and with wait lists, it can happen.
Some rooms, like AKV concierge, is difficult for even owners who call right at 11 months since there are only 5 rooms, so getting those at 7 months is nearly impossible.
IMO, buy at a resort that you will be okay with staying at, providing you will be booking during your home resort period, so that if where you want to try at 7 months is not available, then you will at least be at a place you enjoy.
I own at BLT and BWV because I enjoy those resorts and book each and every stay. If you don't ever plan to book prior to 7 months, then home resort is of less importance.
And, 7 month availability and booking even at 6 months out can make a big difference.
Good luck!