If buying from Disney, you'd get Saratoga Springs, which seems to have great availability, as it is not sold out yet (of course it isn't completely built yet either!)
Getting into Saratoga Springs at 11 months out shouldn't be a problem ever. Getting into another resort at 7 months can be, especially at the smaller resort (BCV, VWL).
Personally, we had no trouble getting a 2BR or 1BR at BCV in June, and a studio at VWL in late September (first
MNSSHP). We've only been members for 2 years, so can't give you more examples than that! We will try in May to switch to a 2BR at VWL from SSR for December - expecting that to be tricky.
If you envision going at least once a year for the next 10-15 years,
DVC is a no brainer, IMHO. If you would normally stay at Deluxe on site, it'll probably pay for itself after the first 40 nights or so.
We already see a benefit that we didn't anticpate fully. Since we have DVC and annual passes (because of the DVC discount), a short trip to WDW is much more feasible (especially coupled with our Southwest Rapid Rewards). We basically went to MNSSHP for just the cost of the tickets to the party, food and souvenirs. So for about the cost of doing some museums locally on a weekend, we had a blast at WDW (not of course including the sunk cost of DVC - but that is sunk after all - had we not gone, it would have been the same!)
My advice - sit down at a spreadsheet and make up a fantasy vacation schedule - what you expect to do in the next ten years. Total it up, adding maybe 5-10% to WDW room rates per year. Compare that to DVC. It might not pay off in those 10 years, but I bet it'll be close - and then don't forget the 36 years after that! Might even pay for your grandkids to go.